Article

The Terrain Analysis System: A tool for hydro-geomorphic applications

March 2005
Hydrological Processes 19(5):1123 - 1130

Authors:

University of Guelph

Much progress has been made in extending the hydro-geomorphic modelling toolbox as a result of developments in the field of digital terrain analysis, also known as geomorphometry (Wilson and Gallant, 2000; Pike, 2002). The enhancement of computer technologies and the widespread availability of digital elevation models (DEMs) since the early 1990s have impacted environmental modelling greatly (Pike, 2000). Geographical information systems (GISs) are now widely applied in hydrology and geomorphology to automate basin, hillslope, and stream network analyses. Several commercial GIS packages have incorporated more common terrain attributes (e.g. slope, aspect, curvature, and wetness index) and terrain analysis procedures (e.g. basin and stream network extraction). These software packages are, however, often prohibitively expensive. Furthermore, whilst commercial GIS packages often contain basic terrain analysis capabilities, very few possess the flexibility and advanced functionality needed by researchers. Several terrain analysis packages have been developed for this purpose, e.g. ANUDEM (Hutchinson, 1989), TARDEM/TauDEM (Tarboton, 1997), LandSerf (Wood, 1998), TAPES (Moore et al., 1991; Gallant and Wilson, 1996), LANDLORD (Florinsky et al., 2002), and DiGeM (Conrad, 2002), some of which are freely available. Unfortunately, many terrain analysis packages lack the visualization and general spatial analysis capabilities of a GIS, or have been developed as extensions to existing commercial software. Additionally, although many terrain analysis packages possess the advanced functionality needed by researchers, they are often difficult to use and, therefore, remain inaccessible to nonexperts. The Terrain Analysis System (TAS) was designed to meet the research needs of government and academic scientists while being simple enough in operation to be used for student instruction. TAS is a stand-alone GIS that possesses much of the spatial analysis functionality typically found in GIS packages. However, it is also capable of advanced modelling of catchment processes. The following is a brief description of TAS’s functionality for applications in hydrology and geomorphology.

Ecological land classification and soil moisture modelling in the boreal forest using LiDAR remote sensing

Thesis

Full-text available

Dec 2010

Meg Southee

Ecological land classification (ELC) is used to classify forest types in Ontario based on ecological gradients of soil moisture and nutrient fertility determined in the field. If ELC could be automated using terrain surfaces generated from airborne Light Detection and Ranging (LiDAR) remote sensing, it would enhance our ability to carry out forest ecosite classification and inventory over large areas. The focus of this thesis was to determine if LiDAR-derived terrain surfaces could be used to accurately quantify soil moisture in the boreal forest at a study site near Timmins, Ontario for use in ELC systems. Analysis was performed in three parts: (1) ecological land classification was applied to classify the forest plots based on soil texture, moisture regime and dominant vegetation; (2) terrain indices were generated at four different spatial resolutions and evaluated using regression techniques to determine which resolution best estimated soil moisture; and (3) ordination techniques were applied to separate the forest types based on biophysical field measurements of soil moisture and nutrient availability. The results of this research revealed that no single biophysical measurement alone could completely separate forest types; furthermore, the best LiDAR-derived terrain variables explained only 36.5% of the variation in the soil moisture in this study area. These conclusions suggest that species abundance data (i.e., indicator species) should be examined in tandem with biophysical field measurements and LiDAR data to improve classification accuracy. iii

Lineament depth deduction using geomorphometry and 3D Euler solution

Article

Feb 2024
ACTA GEOPHYS

In this paper, we present a novel method for determining the depth of lineaments using satellite gravity data, which we test in the Sahel of Sfax area (eastern Tunisia). This region has a relatively flat topography with few significant discontinuities at the surface. As a first step, we used morphometric indices such as slope, aspect, and hydrographic network, calculated from SRTM DEM, to generate separate lineament maps. We then combined these lineaments into a synthetic lineament map, one that showed to be highly consistent with the Bouguer anomaly map deduced from satellite gravity data and the results of similar studies with gravity and seismic geophysical data. The lineament map was then refined and confirmed thanks to field data. These lineaments were later combined with the 3D Euler solution map, and their depth classification was deduced. These results demonstrate both the accuracy of the proposed method as a way to assess lineament depth and its ability to provide valuable information about an area's subsurface geology. This method can be useful for mineral exploration, hydrocarbon exploration, and geohazard assessments.

An Overview of Morphometry Software Packages, Tools, and Add‐ons

Chapter

Jan 2023

The objective of this study is to invent popular, ever‐increasing tools and software that can be used for computing morphometric parameters. We primarily present popular morphometric tools and software aiming to ease the search for such tools by those researchers and scientists who find their new interest in morphometry. With the advances in quality and quantity of digital elevation models, the field of geomorphometric tools, add‐ons, and software has witnessed a new level in the evolutionary phase. The advancement of remote‐sensing methods is making available a plethora of remotely sensed data more effortless with time. Therefore, the demand for the availability of tools for processing such data is also increasing at an equal pace. It is essential to understand the evolution of the tools so that both professionals and newcomers in the field are aware of the capabilities of the tools as well as their developmental aspects. This chapter is oriented toward this approach by providing a collection and a brief overview of morphometric tools developed and ameliorated during the first two decades of the 21st century. The tools being considered here are based on incorporating the concepts of geomorphometry, and thus this chapter begins with a brief introduction to the basic concept of geomorphometry. A basic level of understanding of the subject is desirable for the reader to realize the significance of the tools described here.

Modelling water budget at a basin scale using JGrass-NewAge system

Thesis

Full-text available

Apr 2016

Wuletawu Abera

Water resources availability and its variability is one of the most pressing global problems. Hydrological models are useful to understand the water balance of a basin, providing information for water resource forecast, assessment, and management. The effectiveness of the models in estimating the freshwater space-time availability and variability, however, depends on concurrent and explicitly modelling of all water budget components instead of a single component estimation and optimisation. The whole water budget modelling at basin scale requires a combined solution from hydrological and spatial information tools, in-situ and remote sensing data. The present dissertation describes an effort to improve estimation of each water budget component, and water budget closure at various spatial and temporal scales, by combining JGrass-NewAge model system, GIS spatial toolbox, in-situ and remote sensing data. JGrass-NewAge is a system which deploys modern informatics to facilitate models maintainability and reproducible research. It integrates advanced GIS features and the Object Modelling System version 3 infrastructures, which allow for a component-based modelling experience. This means that JGrass-NewAGE is not actually a model, but a set of elements (the components) that can be combined just before runtime to produce various modelling solutions. Topics like calibration of processes, the interpolation forcing and the assessment of forecasting errors can therefore be faced with consistent and solid approaches. In this context also the use of some remote sensing resources can be inserted appropriately and with new techniques. For all the analysis, two significantly different basins, in terms of size and hydrological processes, are considered as case studies. These are Posina river basin in northeast Italy (small size basin) and Upper Blue Nile basin (large size basin) are used as case study. The uDig Spatial Toolbox (uST) GIS infrastructure that is used for generating the hydromorphological parameters is described in the second chapter. A large number of tools are included in uST for terrain analysis, river network delineation, and basin topology characterisation. In addition, the geomorphological settings necessary to run JGrass-NewAGE are shown. The third chapter studies the effect of spatial discretisation and the hillslope size on basin responses. The possible epistemic uncertainty exerted by the use of sub basin spatial discretisation of topographic information in the semi-distributed hydrological modelling has been studied. The use of different spatial representation in hydrological modelling context has been also studied by comparing JGrass-NewAGE with a model configuration called PeakFlow. The latter is an implementation of the geomorphological unit hydrograph based on the width function. The experiment indicates that the Peak-Flow model, with a more accurate spatial representation, reproduce the storm events slightly better than the JGrass-NewAGE model. In the fourth chapter, the thesis set-up JGrass-Newage modelling solution for the estimation of hydrological modelling inputs (rainfall, snow, temperature data) and estimates them, as well as with their errors. Regards to the meteorological forcings (mainly temperature and precipitation), in Posina river basin where there are relatively dense meteorological stations, the effects of different interpolation schemes were evaluated. Since the hydrological processes from rainfall is different from snowfall, a new method of separating rainfall and snowfall was introduced using MODIS imagery data. In the fifth chapter, JGrass-NewAGE was used to estimate the whole set of water balance components. For evapotranspiration (ET) estimation, the Priestley-Taylor component of JGrass-NewAGE is used. In order to calibrate its parameter a new method based on the water budget was implemented. This method uses two different hypothesis on available data (budget stationarity "Budyko hypothesis", and local proportionality of actual evapotranspiration to soil moisture availability). Finally the spatial and temporal dynamics of water budget closure of Posina river basin is presented. The sixth chapter concerns about the inputs data, particularly precipitation, for water balance modelling in a region where ground-based gauge data are scarce. Five high-resolution satellite rainfall estimation (SRE) products were compared and analysed using the available rain gauge. The basin rainfall is investigated systematically, and it was found that, at some locations, the difference in mean annual rainfall estimates between these SREs very high. In addition to the identification of the best performing products, the chapter shows that a simple empirical cumulative distribution (ecdf) mapping bias correction method can provide a means to improve the rainfall estimation of all SREs, and the highest improvement is obtained for CMORPH. In the seventh chapter, using the capability of JGrass-NewAGE components and different remote sensing data, the spatio-temporal water budget of Upper Blue Nile basin is simulated. The water budget components (rainfall, discharge evapotranspiration, and storage) were analysed for about 16 years at daily time step using the modelling solution and remote sensing data set. For the verification of the approaches followed, wide ranges of remote sensing data (MODIS ET product MOD16, GRACE, and EUMETSAT CM SAF cloud fractional cover) are used. The general conclusion, chapter eight, is presented to draw the overall summary of the thesis and establish the significance of the work.

How to extract river networks and catchment boundaries from DEM. a review of digital terrain analysis techniques

Article

Full-text available

Jan 2009

Vojtěch Barták

Mapping Complex Landslide Scars Using Deep Learning and High-Resolution Topographic Derivatives from LiDAR Data in Quebec, Canada

Article

Full-text available

Oct 2024

Assessment of Net Erosion and Suspended Sediments Yield within River Basins of the Agricultural Belt of Russia

Article

Full-text available

Sep 2022

The SEA/Balance (soil erosion–accumulation balance) model and the WATEM/SEDEM model both mapping the erosion–accumulation budget of sediment within river basins were tested for 11 river basins of the eastern Russian Plain. The dynamics of river sediment yield were evaluated within one of the river basins. The analysis is based on observations of suspended sediment yield in test river basins with an area ranging from 100 to 1500 km2. The maps of the average annual erosion–accumulative budget of sediment were constructed using two methods, making it possible to quantitatively assess the amount of sediment yield from the catchment area for the river basins under study. The WATEM/SEDEM model and the author’s SEA/Balance model were used for sediment yield estimation. The results of calculation using the WATEM/SEDEM model have an average bias of +11% compared to observed suspended sediment yield. The corresponding value in the case of the SEA/Balance model application is −29%. SEA/Balance model assessment sediment yield dynamics for the Sterlya river basin show an 11 percent reduction. It is possible to conclude that the proposed method of SEA/Balance can be applied to river basins of the agricultural zone of the east Russian Plain.

Impact of geomorphometric parameters on the occurrence and distribution of landslides in Yamuna River Basin, North-Western Himalaya, India

Article

Jul 2022
J MT SCI-ENGL

The majority of landslides in the Indian Himalayas are triggered by rainfall and earthquake. The geology and geomorphology also play an important role and constitute the major predisposing factor controlling landslides. Additionally, active tectonics modify the landscape, impacting the occurrence and distribution of landslides. The objective of this study is to investigate the role of some of the major predisposing factors to assess landslide patterns in the Yamuna River Basin as it is prone to recurrent landslide hazards. The approach mainly deals with the application of geographical information system-based statistical analysis and quantifying frequency-area distribution of rainfall-triggered landslides for the years 2015 to 2017. The analysis shows that the frequency of landslides is highest in the slope range 40 o-70 o and the mean landslide size is higher in the slope range 0 o-20 o and 30 o-40 o , remaining constant on further increase in slope angle. The study shows that some critical slope range controls both the frequency and size of landslides. Landslides were mostly restricted to south facing slopes. About 91% of the landslide occur in the drainage density range of 1.2 to 2.1 km/km 2 while landslides show very low occurrence in either lower (<1.2) or higher (>2.1) drainage density. Frequency-size distribution analysis of landslides depicts a distinct cutoff point but an indistinct rollover point. Under-sampling of small landslides can be a reasonable cause for this. Like other studies, the present data fits very well for medium and large landslides following an inverse power law with a scaling exponent of-2.16. Around 80% of landslides are smaller than the cutoff size and 20% larger than this value. The geology and tectonics of Lesser Himalayas and Sivaliks offer favorable conditions for frequent landslides. Areas such as Dehradun, Uttarkashi, Sirmaur, Shimla, and Solan are very prone to landslide activity owing to the presence of 2 poorly consolidated sandstone, conglomerate, quartzites, phyllites, etc. Moreover, the majority of larger landslides are in the Dehradun district where precipitation, drainage density, and lithology are highly favorable to trigger large events. The present study has identified the critical range of predisposing factors responsible for landslides and presents the frequency-size distribution of landslides in the Yamuna River Basin. These are the key inputs in landslide susceptibility mapping and risk assessment. Therefore, the findings from the present analysis can be very helpful in landslide risk reduction and landslide hazard zonation and probably plan critical locations for installation of early warning signals.

Detection of Potential Vernal Pools on the Canadian Shield (Ontario) Using Object-Based Image Analysis in Combination with Machine Learning

Article

May 2021

Vernal pools are small, temporary, forested wetlands of ecological importance with a high sensitivity to changing climate and land-use patterns. These ecosystems are under considerable development pressure in southeastern Georgian Bay, where mapping techniques are required to inform wise land-use decisions. Our mapping approach combines common machine learning techniques [random forest, support vector machines (SVMs)] with object-based image analysis. Using multispectral image segmentation on high-resolution orthoimagery, we first created objects and assigned classes based on field collected data. We then supplied machine learning algorithms with data from freely available sources (Ontario orthoimagery and Sentinel 2) and tested accuracy on a reserved dataset. We achieved producer’s accuracies of 85 and 79% and user’s accuracies of 78 and 84% for random forest and SVMs models, respectively. Difficulty differentiating between small, dark shadows and small, obscured pools accounted for many of the omission and commission errors. Our automated approach of vernal pool classification provides a relatively accurate, consistent, and fast mapping strategy compared to manual photointerpretation. Our models can be applied on a regional basis to help verify the locations of pools in an area of Ontario that is in critical need of more detailed ecological information.

Watersheds and Drainage Networks

Article

Apr 2021

The use of filters based on the Fast Fourier Transform applied to DEMs for the objective mapping of karstic features

Article

Apr 2021
GEOMORPHOLOGY

The suitability of Fast Fourier Transform (FFT) filters to delimit the objective location of geomorphic references is analysed for the case of karstic landscapes, where altitudes feature marked differences. From aerial images and a Light Detection and Ranging (LiDAR) derived high-resolution digital elevation model (DEM), a digital database was created, segregating two geomorphic domains according to scale: domain A (macroforms) and domain B (mesoforms), both subdivided in zones of positive and negative relief polarity. In order to minimise the producer error, the correspondence between the DEM morphology and the features mapped was generalised and certified in a test area, reducing ground truth uncertainty. The efficiency of FFT filters was compared against the most commonly referenced in the literature, such as convolution and openness, in terms of computation cost and geometric position. Two types of FFT filters were created modifying the radius of the high pass mask: short radius filters (appropriate to objectivise macroforms); and middle-large radius filters (appropriate for mesoforms) like convolution and openness. The FFT geomorphic reference obtained offers similar geometric patterns to other filters, but reduced computation times. Moreover, the filters reduce the positional uncertainty of geomorphic contacts, without changing the general altitude trend. The generation of FFT filtered references, combining short and middle-large radius, permits objective mapping of karstic landscapes using a DEM.

ScanGIS'2007 - Proceedings of the 11th Scandinavian Research Conference on Geographical Information Science, Ås, Norway, 5-7 September 2007

Book

Full-text available

Sep 2007

ScanGIS'2007 - Proceedings of the 11th Scandinavian Research Conference on Geographical Information Sciences

Morphology of Khorgo Volcano Crater in the Khangai Mountains in Central Mongolia

Article

Full-text available

Jun 2020

Cenozoic basalt, which is widespread in Mongolia, has been attracting the attention of Central Asian researchers since the beginning of the last century. This study identified the geomorphological shape of the Khorgo volcano. The main purpose of the study is to determine the origin and morphological form of Khorgo volcano, a key representative of Cenozoic volcanism. In general, there are several types of morphological forms associated with lava overflow, and it is important to determine which types are the most common and also to establish a link between them. Geomorphological studies in this area have not been conducted in Mongolia. Spatial improvement and morphometric methods satellite imagery had identified Khorgo volcanic faults. Khangai magmatism had thinned its crust to 45 km during the Tariat-Chuluut volcanic activity. It can be concluded that this was due to the thinning of the continental crust in the Khangai Mountains because of mantle plume. During this time, tectonic faults formed were formed, which had broken through the earth's crust. Part of this fault was formed in the vicinity of Khorgo Mountain from northwest to southeast, and lava flowed with the basic composition, which led to the formation of the current morphological form of Khorgo volcano. The lava flow was less than 45% silica and potassium-dominated, which blocked the Suman River valley and formed the present-day Terkhiin Tsagaan Lake. The morphometric analysis compared the morphology of a typical volcano, which showed that the mouth of the crater of the Khorgo volcano has a slope slanting about 45 degrees, it is about 100 meters in depth, with a diameter of about 500 meters. By comparing the basalt composition of the Khorgo volcano and its morphometric characteristics with other standard volcanoes, it has been determined that it is in the form of a lava dome.

Morphology of Khorgo Volcano Crater in the Khangai Mountains in Central Mongolia

Article

Full-text available

Jun 2020

Satellite-based mapping of near-surface and surface water in the Prairie Pothole Region of Central Canada

Thesis

Full-text available

Jul 2010

Tekleab S. Gala

he Prairie Pothole Region occupies a large portion of North American Great Plains and is characterized by millions of depressions (potholes) that form wetlands. Although the wetlands have various hydro-ecological and socio-cultural functions and services, they are under immense pressure from the impacts of land use and climate change. Therefore, there is a need to characterize these wetlands, not only to understand their services and functions but also to design management practices for effective wetland protection and restoration. Wetlands are often characterized using surface and near-surface hydrological data acquired in situ or via remote sensing observation. In this research, the in situ-measured hydrological data was able to characterize the variability of near-surface hydrology in the Prairie Potholes Region of Central Canada. However, owing to the limitations of in situ measurements, the research established functional relations between remote sensing (RADAR/LiDAR) and near-surface hydrological data. Empirical models developed from these relationships effectively mapped aerial soil moisture and monitored regional and local soil moisture dynamics during the snow-free periods. Furthermore, a more accurate way of delineating prairie wetlands, classifying wetland types and monitoring the wetland boundary changes, IS explored using integrated RADAR/LiDAR/optical data. In conclusion, the research has produced a novel mapping and monitoring technique and results that significantly advance the understanding of hydrodynamics and important hydrologic controls of wetlands and the surrounding uplands at various spatial scales.

Določanje erozije v gričevjih severovzhodne Slovenije z Gavrilovićevo enačbo

Article

Full-text available

Dec 2019

Preučevanje intenzivnosti erozijskih procesov spada med temeljne in pogosto obravnavane geomorfološke dejavnosti ter običajno vključuje tako terenske meritve kot tudi računalniško modeliranje. V Sloveniji so terenske meritve redke, zato prevladuje modeliranje erozijskih procesov. Pri slednjem je zaradi svoje preprostosti kljub pomanjkljivostim zelo priljubljena Gavrilovićeva enačba v več različicah. V prispevku predstavljamo uporabnost geografskih informacijskih sistemov pri izračunu posameznih členov Gavrilovićeve enačbe. Z njeno pomočjo smo za panonska gričevja severovzhodne Slovenije ocenili intenzivnost erozije. // The study of the intensity of erosion processes is one of the fundamental and often treated geomorphological activities. It usually involves both field measurements, as well as computer modelling. In Slovenia, field measurements are rare, so modelling of erosion processes prevail. Due to its simplicity the Gavrilović equation (and its derivatives) is very popular for the calculations of erosion; despite its shortcomings. The paper presents the usefulness of geographic information systems in the calculation of individual parameters of Gavrilović equation. The Gavrilović equation was used to calculate the intensity of erosion in Pannonian low-hills of north-eastern Slovenia.

Sink Removal from Digital Elevation Model–A Necessary Evil for Hydrological Analysis

Article

Full-text available

Nov 2019
CURR SCI INDIA

The present study involves a comparative appraisal of three different sink removal algorithms. The publicly available shuttle radar topographic mission (SRTM) digital elevation model (DEM) version 3.0 of 90 m resolution was used as input DEM. Three sink filling algorithms proposed by Jennson and Domingue (JD), Planchon and Darboux (PD), and impact reduction approach by Lindsay were evaluated for their efficiency in removing the sink from SRTM DEM with minimum alteration of original DEM quality. Various primary and secondary parameters were used for comparative assessment. It was found that all the three algorithms altered the originality of the DEM significantly, but to a different extent. It was found that the PD method of sink removal was better than the other two methods studied here. However, the results also substantiated that the hydrologist must take due care to minimize any uncertainty that might arise due to DEM preprocessing. Keywords: Digital elevation model, hydrological pre-processing, sink filling algorithms, terrain analysis system. DIGITAL elevation model (DEM) is a two-dimensional array of pixels, with each pixel corresponding to elevation values, representing points of the earth's topography. This raster DEM is considered as one of the most valuable data for GIS-based hydrological analysis and allied application at catchment scale 1. Automated hydrological feature extraction using DEM is increasingly gaining popularity because of the availability of high-resolution DEM in public domain 2. The extraction of hydrological features from DEM is not only accurate, but also less time-consuming. However, automated extraction of hydrological features using DEM needs the removal of depression (sink) from the DEM surface. Sink, an inherent artefact, is a spurious pixel which has elevation value lower than its surrounding pixels (i.e. no outlet facilitating the movement of water down slope). It is thus a spatially struc-tured error of a systematic nature and is often associated with the production of DEMs. However, in high resolution , DEM, sink may also arise due to man-made features such as bridges, weirs, culverts, dams, roadways and so on. Thus, removal of surface depression (sink) is an important preprocessing task in hydrological application of DEM 3,4. A number of depression removal methods have been developed which generally differ with respect to depression treatments (artefact or true landscape feature), origin (elevation overestimation or underestimation), the size of scan window and the scan direction used. Some of the sink removal algorithms are purely based on depression filling 5-7 and breaching of elevated pixels 3 or combined filling and breaching operation 8. However, none of these methods are perfect and they alter the original elevation values in DEM to a different magnitudes depending on the nature/complexity of the catchment topography 9,10. In recent times, although few researchers have attempted to evaluate the effects of various sink removal algorithms 11-14 , the results were not that promising to derive any universally accepted conclusion thereof, and this necessitates further investigation on the stated problem. Keeping in view the above facts, the present study aimed at a comparative assessment of three most commonly used algorithms namely Jenson and Domingue (JD) method 5 , Planchon and Darboux (PD) method 7 , and Lindsay and Creed method 8 regarding their effectiveness in removing sink on the DEM surface. The study site for the present research work was Mai-thon reservoir catchment (85.41°-86.90°E long. and 23.75°-24.56°N lat.), which is situated in Jharkhand state, India. The watershed covers an area of about 5553 sq. km. The elevation ranges from 120 to 1360 m above mean sea level. It is predominantly an agricultural watershed with a scattered area of active mines and sparsely distributed forest patches. The source DEM used for this study was shuttle radar topographic mission (SRTM) DEM. SRTM DEM of 3 arc second version 3 (http://srtm.csi.cgiar.org) was down-loaded from Consultative Group on International Agricultural Research-Consortium for Spatial Information (CGIAR-CSI) 15 and clipped for the Maithon reservoir catchment. The sink can be removed either by filling methods or breaching methods or by the combination of both. In the present study, the depression or sink in DEM were removed using following three sink removal algorithms implemented in terrain analysis system (TAS) which is now available as open-source software in the name of Whitebox Geospatial Analysis Tools 16. Jenson and Domingue (JD) method 5 is a sink removal algorithm which typically identifies local minima and then attempts to fill them in an iterative fashion bottom-to-top by exploring each cell's neighbourhood to find outlets. It follows a two-step process for removing the sink. The first step fills all single-cell sinks by keeping their elevation to the lowest elevation of their neighbours (i.e. pour points). The second step fills complex sinks of

Assesment of morphometric and hydrological properties of smalls watersheds in East Java Regions

Article

Full-text available

Aug 2019

Artikel ini menyajikan identifikasi, penilaian dan visualisasi sifat fisik, topografi, morfometrik dan hidrologi daerah aliran sungai kecil di Wilayah Jawa Timur. Empat puluh empat (44) DAS digunakan untuk analisis. Sifat fisik (yaitu, jenis tanah dan penggunaan lahan) diperoleh dengan memotong lapisan GIS dengan batas daerah aliran sungai. Kemudian ASTER G-DEM2 digunakan untuk menurunkan sifat morfometrik daerah aliran sungai. Selain itu, sifat hidrologis diperoleh dengan menganalisis data curah hujan dan debit yang tersedia. Parameter yang dipilih adalah untuk mewakili setiap properti daerah aliran sungai. Akhirnya, korelasi sederhana antara sifat-sifat fisik, topografi, morfometrik, dan hidrologi daerah aliran sungai. Hasil penelitian menunjukkan bahwa beberapa DAS menunjukkan kesamaan dan perbedaan pada parameter morfometrik dan hidrologi.

Review on algorithms of dealing with depressions in grid DEM

Article

Full-text available

Apr 2019

Depressions in grid digital elevation models (DEMs) need to be dealt with before the topographic attributes (such as specific catchment area) and terrain features (such as drainage networks) related to flow directions can be derived from DEMs in a hydrologically-correct manner. Many depression-processing algorithms, which adopt different strategies and take different information under consideration for determining correct flow directions in depressions, have been proposed. However, currently, there is still no one algorithm which can satisfactorily deal with depressions in grid DEMs under various application contexts. In this paper, we review existing depression-processing algorithms based on the adopted strategies (i.e. the DEM-revising strategy and the DEM-unchanging strategy). Algorithms with the DEM-revising strategy especially are discussed in detail according to their designs relating to the revision of DEM elevations, i.e. the smoothing filter, depression filling, depression breaching (or carving), using other qualified data, and applying different algorithms to depressions with different characteristics. Existing ways of improving the computation efficiency of depression-processing algorithms are also presented, i.e. serial algorithm optimization and parallel algorithms. Lastly, we discuss a possible design for an optimal depression-processing algorithm which may be developed in the future.

GIS-based spatial prediction of debris flows using logistic regression and frequency ratio models for Zêzere River basin and its surrounding area, Northwest Covilhã, Portugal

Article

Full-text available

Sep 2018

Landslide susceptibility mapping (LSM) is important for catastrophe management in the mountainous regions. They focus on generating susceptibility maps beginning from landslide inventories and considering the main predisposing parameters. The aim of this study was to assess the susceptibility of the occurrence of debris flows in the Zêzere River basin and its surrounding area using logistic regression (LR) and frequency ratio (FR) models. To achieve this, a landslide inventory map was created using historical information, satellite imagery, and extensive field works. One hundred landslides were mapped, of which 75% were randomly selected as training data, while the remaining 25% were used for validating the models. The landslide influence factors considered for this study were lithology, elevation, slope gradient, slope aspect, plan curvature, profile curvature, normalized difference vegetation index (NDVI), distance to roads, topographic wetness index (TWI), and stream power index (SPI). The relationships between landslide occurrence and these factors were established, and the results were then evaluated and validated. Validation results show that both methods give acceptable results [the area under curve (AUC) of success rates is 83.71 and 76.38 for LR and FR, respectively]. Furthermore, the AUC results for prediction accuracy revealed that LR model has the highest predictive performance (AUC of predicted rate = 80.26). Hence, it is concluded that the two models showed reasonably good accuracy in predicting the landslide susceptibility in the study area. These two models have the potential to aid planners in development and land-use planning and to offer tools for hazard mitigation measures.

Efficiency of local minima and GLM techniques in sinkhole extraction from a LiDAR-based terrain model

Article

Jul 2018

The aim of this paper was to study reliable automated delineation possibilities of karst sinkholes using a LiDAR-based digital terrain model (DTM) with pixel-based classifications. We applied two approaches to extract sinkholes: (1) general linear modeling (GLM) with morphometric indices derived from DTM; (2) and a local minima-based delineation using only LiDAR DTM as the input layer. The outcome of the local minima was significantly different from the reference ones but found all the sinkholes without previous knowledge of the area. The GLM-based outcome did not differ statistically from the reference. Results showed that these approaches were efﬁcient in detecting sinkholes based on LIDAR derivatives, and can be used for risk assessment and hazard preparedness in karst areas: GLM had an overall accuracy of 89.5% and local minima had an accuracy of 92.3%; both methods identified sinkholes but also had commission errors, identifying depressions as sinkholes.

Detection of gullies in Fort Riley military installation using LiDAR derived high resolution DEM

Article

Full-text available

Mar 2018

Intensive use of military vehicles in military installations create conditions favorable for gully formation. Gullies impede the access of vehicle, restrict the continuation of training, and lead to significant damage to vehicle and risk the life of soldiers. Therefore, it is critical to correctly identify the locations of gullies for continuous training mission. In this study, Fort Riley (FR) military installation was chosen as the study area. LiDAR derived 1 m resolution digital elevation model (DEM) acquired on 2010 was used to map the gullies. A procedure that measures local topographic position, i.e., difference from mean elevation (DFME) along with its integration to the land surface having high surface curvature values was employed. Two high spatial resolution WorldView-2 images of 2010 and field gully data collected in 2010 were utilized for accuracy assessment. Results showed that: (1) A total of 237 small and 166 large gullies were detected and most of them dominated the central west and northwest parts of the installation; (2) Based on the visual interpretation in the WorldView-2 images, there was no statistically significant difference between the detected and observed numbers of gullies; (3) Gullies measured in the field were well detected with an overall accuracy of 78%.

Natural Hazards and Earth System Science

Article

Jan 2007

Yuei-An Liou

This study anatomized algorithm effects of specific contributing area (SCA) on soil wetness estimation, consequently landslide prediction, in SHALSTAB. A subtropical mountainous catchment during three typhoon invasions is targeted. The peak 2-day rainfall intensity of the three typhoons: Haitang, Mindulle and Herb are 144, 248 and 327 mm/day, respectively. We use modified success rate (MSR) to retrieve the most satisfying mean condition for model parameters in SHALSTAB at three rainfall intensities and respective pre-typhoon NDVI themes. Simulation indicates that algorithm affects the prediction of landslide susceptibility (i.e. FS, Factor of Safety) significantly. Based on fixed NDVI and the mean condition, we simulate by using full scale rainfall intensity from 0 to 1200 mm/day. Simulations show that predicted unstable area coverage increases non-linearly as rainfall intensity increases for all algorithms yet with different increasing trends. Compared to Dinf, D8 always gives lower coverage of predicted unstable area during three typhoons. By contrast, FD8 gives higher coverage areas. The absolute difference (compared to Dinf) in predicted unstable area ranges from ∼−3% to +4% (per-cent watershed area). The relative difference (compared to Dinf) ranges from −15% to as high as +40%. The maximum absolute and relative differences in unstable area prediction occur around the condition of 100-300 mm/day, which is common in subtropical mountainous region. Theoretical relationship among slope, rainfall intensity, SCA and FS value was derived in which FS values are very sensitive to algorithms in the field of slope from 37 to 52degree. Results imply any comparison among SCA-related landslide models or engineering application of rainfall return period analysis must base on the same algorithm to obtain comparable results. This study clarifies the SCA algorithm effect on FS prediction and deepens our understanding on landslide modeling.

Detection of gullies in Fort Riley military installation using LiDAR derived high resolution DEM

Article

Full-text available

Mar 2018
J TERRAMECHANICS

Automated Techniques to Identify Lost and Restorable Wetlands in the Prairie Pothole Region

Article

Full-text available

Sep 2017

Wetland loss in the Prairie Pothole Region has been substantial, and automated techniques to estimate wetland loss and identify priority wetlands for restoration are crucial if important ecosystem services provided by wetlands are to be maintained. A suite of automated methods was developed to establish a historical wetland inventory and to identify the proportion of permanently and temporarily lost wetlands in a prairie pothole watershed in Alberta, Canada. A power law analysis of area vs. frequency of historical wetlands provided estimates of permanently lost wetlands. Combining the historical wetland inventory with an inventory of existing wetlands provided estimates of temporarily lost wetlands. 22,204 historical wetlands comprising 12,431 ha were estimated in the watershed. Permanently lost wetland number and area were estimated as 11.1% and 0.6% respectively, and temporarily lost wetland number and area were estimated as 61.1% and 78.3% respectively. Existing wetlands represented only 27.8% of the total historical number and 21.2% of the total historical area. 1,588 ditch-drained (relatively easy restore) wetlands were identified from the inventory of temporarily lost wetlands using digital terrain analysis, representing a potential recovery of 7.2% of the historical wetlands by number and 9.8% by area.

Evaluation of different digital elevation models for analyzing drainage morphometric parameters in a mountainous terrain: a case study of the Supin–Upper Tons Basin, Indian Himalayas

Article

Full-text available

Sep 2016

Background: With myriad geospatial datasets now available for terrain information extraction and particularly streamline demarcation, there arises questions regarding the scale, accuracy and sensitivity of the initial dataset from which these aspects are derived, as they influence all other parameters computed subsequently. In this study, digital elevation models (DEM) derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER V2), Shuttle Radar Topography Mission (SRTM V4, C-Band, 3 arc-second), Cartosat -1 (CartoDEM 1.0) and topographical maps (R.F. 1:250,000 and 1:50,000), have been used to individually extract and analyze the relief, surface, size, shape and texture properties of a mountainous drainage basin. Results: Nestled inside a mountainous setting, the basin is a semi-elongated one with high relief ratio (>90), steep slopes (25°–30°) and high drainage density (>3.5 km/sq km), as computed from the different DEMs. The basin terrain and stream network is extracted from each DEM, whose morphometric attributes are compared with the surveyed stream networks present in the topographical maps, with resampling of finer DEM datasets to coarser resolutions, to reduce scale-implications during the delineation process. Ground truth verifications for altitudinal accuracy have also been done by a GPS survey. Conclusions: DEMs derived from the 1:50,000 topographical map and ASTER GDEM V2 data are found to be more accurate and consistent in terms of absolute accuracy, than the other generated or available DEM data products, on basis of the morphometric parameters extracted from each. They also exhibit a certain degree of proximity to the surveyed topographical map. Keywords: SRTM, ASTER, Cartosat, Topographical maps, DEM, Morphometry, Accuracy

A novel topographic parameterization scheme indicates that martian gullies display the signature of liquid water

Article

Nov 2016
EARTH PLANET SC LETT

Martian gullies resemble gullies carved by water on Earth, yet are thought to have formed in an extremely cold (<−50°C) and dry (humidity <100 precipitable micrometers) surface environment (cf. Mellon et al., 2004). Despite more than a decade of observations, no consensus has emerged as to whether liquid water is required to form martian gullies, with some recent studies favouring dry CO2-driven processes. That this argument persists demonstrates the limitations of morphological interpretations made from 2D images, especially when similar-looking landforms can form by very different processes. To overcome this we have devised a parameterization scheme, based on statistical discriminant analysis and hydrological terrain analysis of meter-scale digital topography data, which can distinguish between dry and wet surface processes acting on a landscape. Applying this approach to new meter-scale topographic datasets of Earth, the Moon and Mars, we demonstrate that martian gullied slopes are dissimilar to dry, gullied slopes on Earth and the Moon, but are similar to both terrestrial debris flows and fluvial gullies. We conclude that liquid water was integral to the process by which martian gullies formed. Finally, our work shows that quantitative 3D analyses of landscape have great potential as a tool in planetary science, enabling remote assessment of processes acting on planetary surfaces.

Biophysical indicators based on spatial hierarchy for informing land reclamation: The case of the Lower Athabasca River (Alberta, Canada)

Article

Sep 2016

Whitebox GAT: A case study in geomorphometric analysis

Article

Jul 2016
COMPUT GEOSCI-UK

John B Lindsay

This paper describes an open-source geographical information system (GIS) called Whitebox Geospatial Analysis Tools (Whitebox GAT). Whitebox GAT was designed to provide a platform for the rapid development and testing of experimental geospatial analysis methods, supported by its extensible design, integrated facilities for custom plug-in tool authoring, and its novel open-access design philosophy. One of the unique characteristics of Whitebox GAT is the ease with which users can inspect and modify the algorithms for individual geoprocessing tools. The open-access software model that Whitebox GAT adopts is designed to lessen the barriers that are often imposed on end-users when attempting to gain deeper understanding of how a specific function operates. While Whitebox GAT has an extensive range of GIS and remote sensing analytical capabilities, making it broadly suited for advanced scientific research applications in the Earth Sciences, this paper focusses on the software's application in the field of geomorphometry. An airborne LiDAR data set for a small headwater catchment of the Missisquoi River in northern Vermont, USA, was filtered to identify ground-points and then interpolated into a 2.0 m resolution bare-Earth DEM. The DEM was processed to remove spurious off-ground objects (mainly buildings), to reduce surface roughness under heavy forest cover, and to hydrologically pre-condition the DEM. These data were then used to extract salient hydrological structures, i.e. the stream network and their associated sub-basins.

Spatial Variability in Biomass Yield of Switchgrass, Native Prairie, and Corn at Field Scale

Article

Jan 2015

Evaluating biofuel crop yield and its spatial variability on a field scale is important for determining the proper bioenergy crops suitable for specific lands. Within field spatial variability of switchgrass (Panicum virgatum L.), native prairie mix, and corn (Zea mays L.) biomass yield and its relation to soil properties were investigated in 2011 and 2012 at two farms in southwestern Michigan. At all sites and years, the order of biomass yields was corn > switchgrass > native prairie, which was consistent with fertilization rates of the crops. Short stand age of the perennial grass also contributed to the relatively lower yield. At both sites, switchgrass yield was not significantly different between 2011 and 2012, while corn yield was significantly lower in 2012 than in 2011. For switchgrass, within-field variation was found considerably larger than the variation between years or between sites, while the variation between years or sites were comparable or greater than the within field variation for corn or native prairie. Two factors extracted from partial least square regressions (PLSRs) between biomass yield with soil and topographic variables could explain the majority of within field spatial variation for most of the fields in the study. Weight values of predictor variables from PLSRs were found strongly correlated between the 2 yr for a given crop at the same site with correlation coefficients from 0.65 to 0.89, as well as between switchgrass and native prairie at a given site. © 2016 by the American Society of Agronomy 5585 Guilford Road, Madison, WI 53711 USA. All rights reserved.

Mapping and spatial analysis of suspended sediment yields from the Russian Plain

Article

Jan 2012

The aim of this paper is to demonstrate the potential use of a GIS and associated database to map and analyse global patterns of sediment yield. Attention focuses on the suspended sediment yield (SSY) data available for the European territories of the Russian Federation and the variation of SSY across part of the Russian Plain. A GIS and database have been developed for the Volga River basin. The GIS system permits the drainage basins for which SSY data are available to be delineated and the database conflates information on sediment yield and the hydrological and physiographic characteristics of the individual drainage basins. A map of the variation of annual sediment yield within the Volga basin is presented.

Global geoinformation system "suspended sediment yield in the river basins of the earth"

Article

Full-text available

Jul 2015

General-theoretical and methodical problems of creation and use of the global gcoinformation system, which reflects the basic regularity of formation, spatial and temporal variability of suspended sediment yield of the Earth's rivers, arc considered. The role of river basins as gcosystcm formation in research of sediment yield is shown. Approaches to the automation detection of river basins boundaries, methods of integration geoinformation system with thematic databases for purpose of geomorphological analysis of river suspended sediment yield are offered and tested.

A web-based tool for watershed delineation considering lakes and reservoirs

Article

Sep 2024
ENVIRON MODELL SOFTW

Lakes have significant impacts on watershed hydrology. However, until now, no web-based tool has been available for watershed delineation considering lakes. In this study, we developed a tool to address this, enabling non-exports to delineate watersheds. First, a conceptual data model was proposed to represent related spatial units and their flow relationships, including rivers, lakes, river sub-basins, lake hillslopes, and flow paths. Subsequently, a web-based tool was designed and implemented, which enables users to select an area of interest and obtain watershed delineation results without the need for software installation or data preparation. This tool also supports for the customization of data and parameters. Two case studies, conducted at the Fushi Reservoir and Mahu Lake, demonstrated the system's usability. To our knowledge, this study presents the first web-based tool for watershed delineation that considers lakes, and it has great potential for applications in watershed modeling and management.

Geomorphological Analysis and Hydrological Potential Zone of Baira River Watershed, Churah in Chamba District of Himachal Pradesh, India

Article

Full-text available

Apr 2017

In the present study, an attempt has been made to study the quantitative geomorphological analysis and hydrological characterization of 95 micro-watersheds (MWS) of Baira river watershed in Himachal Pradesh, India with an area of 425.25 Km2. First time in the world, total 173 morphometric parameters have been generated in a single watershed using satellite remote sensing data (i.e. IRS-P6 ResourceSAT-1 LISSIII, LandSAT-7 ETM+, and LandSAT-8 PAN & OLI merge data), digital elevation models (i.e. IRS-P5 CartoSAT-1 DEM, ASTER DEM data), and soI topographical maps of 1: 50,000 scale. The ninety-five micro-watersheds (MWS) of Baira river watershed have been prioritized through the morphometric analysis of different morphometric parameters (i.e. drainage network, basin geometry, drainage texture analysis, and relief characterizes ). The study has concurrently established the importance of geomorphometry as well as the utility of remote sensing and GIS technology for hydrological characterization of the watershed and there for better resource and environmental managements.

Lineament depth deduction using geomorphometry and 3d-Euler solution

Preprint

Full-text available

Jul 2023

In this paper, we present a novel method for determining the depth of lineaments using satellite gravity data, which we test in the Sahel of Sfax area (eastern Tunisia). This region has a relatively flat topography with few significant discontinuities at the surface. As a first step, we used morphometric indices such as slope, aspect, and hydrographic network, calculated from SRTM-DEM, to generate separate lineament maps. We then combined these lineaments into a synthetic lineament map, which showed a high level of agreement with the Bouguer anomaly map derived from satellite gravity data and with previous studies that used geophysical data (seismic and gravity). We also validated the lineament map using field data. By fusing these lineaments with the 3D Euler solution map, we were able to deduce the depth classification of the lineaments. Our results demonstrate the effectiveness of our proposed method in estimating the depth of lineaments and its potential to provide valuable insights into the subsurface geology of an area. This method can be a useful tool for mineral exploration, hydrocarbon exploration, and geohazard assessments.

Algorithm for calculation of basic surfaces based on digital elevation model in SAGA GIS software (on the example of Arkhangelsk Region)

Article

Jan 2023

Geospatial Approach to Identify the Suitable Sites for Water Conservation: I ndian Context

Chapter

Apr 2021

PhD Thesis - GIS Mapping of Soil Erosion Risk On Mauritius Island

Thesis

Full-text available

Jan 2011

Rody Nigel

The numerous estuarine, marshy and marine ecosystems along the coastline of Mauritius Island are potential sinks for sediment, especially during intense rainfall events when accelerated erosion predominates and delivery ratios are high at basin outlets. In this work, a GIS-based (Geographical Information System) soil erosion risk mapping model termed ‘MauSERM’ has been devised to map soil erosion risk on Mauritius. MauSERM employs qualitative data integration and decision rules to produce monthly soil erosion risk maps based on four factors: rainfall depth, soil type, topographic slope length and land cover type, which were parameterised, classified and combined to obtain a gradation of erosion risk at 5 m ground pixel resolution and with five classes ranging from very low to very high. By analysing the spatial and temporal patterns in monthly soil erosion risk, areas with the highest erosion risk were identified, which are referred to as the ‘high erosion areas’ of the Island. Such areas were established as cultivations (sugarcane, tea and vegetables) on erosion susceptible terrain, which have mostly slopes >20% and highly erodible soils. Accordingly, these areas would be the focus for conservation efforts, as they are posing the greatest threats to aquatic ecosystems off-site, while being at risk to on-site land degradation. Thus, the high erosion areas, which constitute 251 km2 or 14% of the Island’s surface area, were coupled with basins and subbasins and analysed against wetlands locations in order to identify priority action basins (and their subbasins) for conservation efforts. Furthermore, by making use of data developed for the erosion risk mapping and the Revised Universal Soil Loss Equation (RUSLE), total soil loss on the Island was estimated at 298,259 t yr-1, with soil loss from high erosion areas totalling 84,780 t yr-1 (28% of total soil loss). If all of the high erosion areas were afforested, their soil loss would be reduced to 10,264 t yr-1, i.e. a reduction of 88% for the high erosion areas and a reduction of 25% for the Island. In fact, the general recommendation is to convert the cultivations of the high erosion areas into planted vegetation or forest in order to reduce soil loss and downstream sedimentation. Thus, future studies will be focused on the high erosion areas, including measurements and modelling, in order to test the proposed conservation strategies for soil erosion reduction, particularly the afforestation or revegetation measures.

The source of terrain slope data is an important consideration for natural resource management: A comparison of field measured and DEM calculated slope values

Article

Jan 2021

On the Ground •Slope is a critical factor in understanding many ecological patterns. •Although a field-based clinometer remains a useful slope evaluation tool, the ease of access and ability to accommodate variable spatial scales associated with digital elevation models (DEMs) makes them a commonly used data source for slope evaluation. •However, DEM and field-based clinometer measures of slope do not characterize topography equally. •Natural resource managers must consider the compatibility of their data before incorporating slope values from different sources for ecological analyses. •Ground truthing of remotely sensed data (i.e., DEMs) is important to ensure the data adequately represent the desired field conditions.

Prioritization of Landslide Effective Factors using Logistic Regression (Case Study: A part of KopeDagh-HezarMasjedZone)

Article

Full-text available

May 2019

Short term Distributed Hydrological Modeling of Gaula catchment

Thesis

Full-text available

Jun 2010

Testing and trying out of the applicability and utility of watershed hydrological models in different; catchment sizes, hydro-geologic conditions, soil conditions and with different time resolutions is necessary for a range of spatial scales to assess the utility of these models in water shade management means like flood protection, land slide prevention, erosion control etc. The main purpose of this thesis is to tryout TOPLAND hydrological model, i.e. the new developments to the LANDPINE model allowing for using TOPMODEL distributed runoff generation, with different precipitation input methods. It focuses on the simulation of precipitation events with time resolution of one hour. Short term time resolution event simulations are important to capture flow events in small and large catchments; since these events are responsible for local flood, land slide etc., especially in areas where they are strongly localized. The model simulation has been carried out using three different precipitation input methods; gauge IDW interpolation, gauge simulated and radar based precipitation data for the selected hourly events of 2006 (27-07-2006 00:00 to 29-07-2006 23:00) and 2009 (19-07-2009 05:00 to 25-07-2009 20:00). 2009 Event The 2009 event is characterized by high peak and uniformly distributed event. For the bias corrected radar precipitation, the objective method of result comparison showed an excellent correspondence between observed and simulated flows with NS (R2 ) of 0.98, correlation (R2 ) of 0.98 and PBIAS of 0.48% at the calibration point (Gaulfoss). The bias corrected radar precipitation also showed a very good performance of the model at the interior uncalibrated gauging stations with average values of NS (R2 ) 0.85, correlation (R2 ) 0.93 and PBIAS 16.6% of the HugdalBru, Lillebudal and Eggafoss gauging stations. The gauge IDW interpolation and gauge simulated precipitation input methods also showed a very good performance of the model both at the calibration and internal uncalibrated gauging stations. 2006 Event The 2006 event is characterized by low peak and unevenly distributed (localized) event. The bias corrected radar precipitation is the only precipitation input method that made possible for calibration of the model. The objective method of result comparison showed a very good result for NS (R2 ) of 0.96, correlation (R2 ) of 0.97 and PBIAS of 5.1% at the calibration point (Gaulfoss). At the internal uncalibrated gauging stations, the correlation and PBIAS showed a good performance with average correlation (R2 ) of 0.77 and PBIAS of 21.3% and a poor average NS (R2 ) of 0.3.

References

Chapter

Feb 2018

John P. Wilson

Stream Network Modelling from Aster GDEM Using ArcHydro GIS: Application to the Upper Moulouya River Basin (Eastern, Morocco)

Article

Full-text available

Jan 2017

This paper discusses the integration between GIS and hydrological models and presents a case study relating to the upper section of Moulouya River Basin (UMRB) situated in the east of Morocco. The Basin is an inland water-shed with a total area of approximately 10,000 km2, stretching in the junction between the Middle Atlas, the High Atlas Mountain and the Middle Moulouya basin. From ArcGIS ArcHydro framework data models, different parameters of the Moulouya River and its catchment area have been defined. DEM based ArcHydro model was run on Aster-GDEM V2 data at a horizontal spatial resolution of 30 meters. Several raster and vector products of the Upper Moulouya River and its catchment area have been defined at the end of the model. Final results of the models were discussed and compared with the reality. These results can be used in baseline for advanced hydrology and geomorphology research on the catchment area. They can support for decision-making on ground and surface water resource, distribution and management.

Three-dimensional morphological analysis method for geologic bodies and its parallel implementation

Article

Jul 2016
COMPUT GEOSCI-UK

It has been found that the spatial locations and distributions of orebodies, especially for certain hydrothermal mineral deposits, are closely related to the shape of intrusive geologic bodies. For complex and large-scale geologic bodies, however, it is challenging to achieve rigorous and quantitative morphological analysis by standard geological surface reconstruction and trend-surface analysis methods. This paper presents a novel, quantitative morphological analysis method for general geologic bodies of closed 2-manifold surface based on mathematical morphology. Through the processes of morphological filtering, set operations and three-dimensional Euclidean distance transform (3D-EDT), the global trend shape, local convex and concave zones as well as degree of surface undulation of a geologic body are extracted respectively. All of the three analysis phases are speeded up via parallel algorithms implemented by using the message passing interface (MPI) standard. The proposed method is tested with a case study of the Xinwuli intrusion with complex shape in Fenghuangshan deposit of the Tongling district, China. The results demonstrate that the method is an effective and efficient way to achieve quantitative morphological analysis, thereby decreasing the time necessary to find the association between morphological parameters of geologic bodies and mineralization.

Legacy soil maps as a covariate in digital soil mapping: A case study from Northern Iran

Article

Jun 2016
GEODERMA

Digital soil mapping (DSM) can be used for updating soil surveys. Legacy soil survey maps are often used as a covariate for updating soil surveys because such soil survey maps are logically assumed to contain significant information about the spatial distribution of soil classes. In the present study the usefulness of including conventional soil survey maps as a DSM covariate was investigated. Random forest and multinomial logistic regression models were built using two different covariate sets: covariate set 1 included the legacy soil survey, covariate set 2 excluded the soil survey. Soil Great Groups, Subgroups, and Series taxonomic classes were modeled using both models and covariate sets for an area of ~ 85,000 ha in Golestan Province, northern Iran. Overall model accuracy, the Kappa statistic, and individual covariate importances were used to assess the influence of including the legacy soil survey. Including the conventional soil map as covariate generally increased model accuracy, but the improvement in model accuracy was surprisingly small at all taxonomic levels. This may be due to soil change or the mapping scale of the legacy soil survey. Random forests was found to be more accurate than multinomial logistic regression at all taxonomic levels. Multinomial logistic regression models at the soil Series level were less accurate than the legacy soil survey.

Assessment of the Sensitivity of Streamflow Simulations to Changes in Patch Resolution Using GIS Based Hydro-Ecologic Model

Article

Full-text available

Jan 2016

Eight different patch configurations were investigated to analyze the effect of patch characteriza-tion/formation in streamflow simulation, using the Regional Hydro-Ecologic Simulation Systems (RHESSys) model. It is investigated for eight different patch configurations of a subcatchment of the Turkey Lakes Watershed, Ontario. The model's hydrological parameters are calibrated for each of these patch configurations and the performance of the simulations is evaluated. Results indicate that both the nature of the flow simulation and the calibrated parameter values are sensitive to patch configuration. The best simulation results were obtained for the patch configuration with the highest spatial variation of climate, stream network and hillslope conditions across the subcatchment. Different patch configurations also lead to markedly different calibrations of the model's hydrological parameters (54.26 < k < 119.13; and 1.02 < m < 2.28), which has implications for the physical interpretation and transferability of the calibrated parameter values.

Hydrologic modeling and evaluation of Best Management Practice scenarios for the Grand River watershed in Southern Ontario

Article

Feb 2016
J GREAT LAKES RES

The Grand River is the largest river in Southern Ontario feeding Lake Erie with water, sediment, and nutrients. Understanding the watershed hydrological processes is crucial to support decision making on reducing non-point source pollution from the watershed into Lake Erie. In this study, the Soil and Water Assessment Tool (SWAT) was adapted to Canadian conditions and applied to the Grand River watershed in Southern Ontario to simulate hydrologic processes based on available geospatial, climate, management, flow, and water quality data. The SWAT was calibrated based on flow, sediment, and nutrient concentrations at eight flow gauging stations and seven water quality stations. The calibrated model was then applied to evaluate the potential effects of Best Management Practices (BMPs) including nutrient management, buffer strip, cover crop, and wetland restoration on water quantity and water quality in the watershed. The evaluated results showed that the BMPs of nutrient management and wetland restoration have more significant impacts on nutrient reduction at the watershed outlet to Lake Erie based on the BMP implementation and extent that were applied in this study. The SWAT modeling, findings, challenges, and recommendations for future research in the Grand River watershed are also discussed in this paper.

Catchment Characterization to Understand Flooding in Cagayan De Oro River Basin in Northern Mindanao, Philippines

Article

Full-text available

Jan 2016

The Cagayan de Oro River Basin is the second largest river basin or watershed in Northern Mindanao, occupying an estimated area of 1,373.84 sq. km. The drainage basin was delineated using Shuttle Radar Topographic Mission (SRTM) 90m digital elevation model (DEM). Geographical features were derived from the DEM using geographic information system (GIS) to perform a morphometric analysis of the river basin and evaluate various parameters of linear, areal and relief aspects. Linear aspect analyses showed that the drainage basin has a 7 th order stream with a bifurcation ratio of 1.8. Areal aspect demonstrates that the basin has a drainage density of 2.29 km/mk2 with a circularity and elongation ratios indicating that the basin is less elongated. Relief aspect of the river basin indicates that it has a resistant basement rock formation and susceptible to erosion. Overall evaluation of the various basin parameters revealed that the inherent features of the river basin has made it naturally liable to flooding with anthropogenic activities exacerbating the extent of risks.

Using DEMs for automatic plotting of catchments

Article

Jan 2014

The authors suggest the method for digital elevation models (DEMs) compiling aimed to plotting the boundaries of the drainage catchments for the lowland relief (West Siberia as an example). The proposed method allows to take into account the local contemporary depressions - traps of the suspended sediment yield and surface runoff. In the result the higher precision of the basins boundaries pattern is obtained. In this method additional information from the topographic maps is used. The DEM compiled with the use of the suggested method helps to significantly increase the accuracy of the West Siberian catchments' automatic plotting.

Geomorphometry: Concepts, Software, Applications

Article

Jan 2008

Primary topographic attributes

Chapter

Full-text available

Jan 2000

Digital Terrain Analysis in Terrain Analysis: Principles and Applications

Chapter

Full-text available

Jan 2000

pdf

A New Procedure for Gridding Elevation and Stream Line Data with Automatic Removal of Spurious Pits

Article

Full-text available

Apr 1989
J HYDROL

M.F. Hutchinson

A morphological approach to the interpolation of regular grid digital elevation models (DEMs) from surface specific elevation data points and selected stream lines is described. The approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm. The drainage enforcement algorithm removes spurious sinks or pits yielding DEMs which may be used to advantage in hydrological process studies. The drainage enforcement algorithm has also been found to significantly increase the accuracy of DEMs interpolated from sparse, but well chosen, surface specific elevation data. Moreover, it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization.

Hill shading and the reflectance map

Article

Full-text available

Feb 1981

Berthold K. P. Horn

Shaded overlays for maps give the user an immediate appreciation for the surface topography since they appeal to an important visual depth cue. A brief review of the history of manual methods is followed by a discussion of a number of methods that have been proposed for the automatic generation of shaded overlays. These techniques are compared using the reflectance map as a common representation for the dependence of tone or gray level on the orientation of surface elements.

Higher isn't necessarily better: visibility algorithms and experiments

Article

Jan 1994

A physically based model for calculating contributing area on hillslopes and along valley bottoms

Article

Dec 2003

John B Lindsay

Most existing methods of calculating contributing area are unable to accurately model the pattern of contributing area on hillslopes and along valley bottoms. This paper describes a new flow algorithm, the adjustable dispersion routing algorithm (ADRA). Rather than calculating contributing area using predetermined flow characteristics that are insensitive to location in the landscape, ADRA predicts channel location and adjusts flow characteristics accordingly. ADRA increases the degree of flow divergence downslope from divides until a channel head is detected. Channel head locations are estimated on the basis of a user-defined threshold of an area-slope function. Therefore the algorithm overcomes the problems of aggregated flow on hillslopes and divergent flow along valley bottoms. The pattern of catchment area produced by ADRA was compared with similar patterns calculated using a similar flow algorithm for a variety of natural landscapes. ADRA produced patterns of contributing area that were more consistent with the theory of channel initiation.

DEM-based depth in sink as an environmental stimator

Article

Mar 2001
ECOL MODEL

The sink as a geomorphological feature can modify a spatial distribution of soil moisture due to the water stagnation in the flood-plain region or spatial distribution of air temperature and humidity (air confluence effect) as well as soil depth in the karstic region. A new variable based on digital terrain model, depth in sink, is introduced as an environmental estimator. The ability of the new variable to explain spatial distributions of the relative presence of dominant tree species is tested in the case study for a karstic region (Europaean Silver Fir, Common Beech, Norway Spruce and Mountain Pine) and for a flood-plain region (Pedunculate Oak and Narrow-leaved Ash), both in Croatia. The general linear modelling method was used. Depth in sink was the significant estimator of the spatial distribution for all tested tree species.

A Bibliography of Terrain Modeling (Geomorphometry), the Quantitative Representation of ��Topography —Supplement 4.0

Article

Jan 2002

RICHARD J. PIKE

Drainage Networks from Grid Digital Elevation Models

Article

May 1991

Current algorithms that deduce the drainage network from a digital elevation model (DEM) represented by a regular array of surface elevations share a fault: Unless the terrain is rugged, the derived water channels tend to flow in parallel lines along preferred directions engendered by the sampling grid orientation. We present a simple solution to the problem. A second difficulty is the presence of noise that creates artificial pits. We briefly describe a method which deals with pits in what we believe to be a more efficient manner for virtual memory environments than previous efforts. Our system has treated DEMs of nearly 9,000,000 pixels. We show how depth first search of the resulting drainage network permits segmentation of the DEM into basins by various criteria, analysis of stream-sediment anomaly dilution profiles, improved hydrological models and other applications.

Advanced Photon Source: Radiological design considerations

Article

Jul 1991

H.J. Moe

The Argonne National Laboratory's Advanced Photon Source (APS) will include a 200 MeV electron linac, a positron converter target, a 450 MeV positron linac, a positron accumulator ring, a 7 GeV booster synchrotron, a 7 GeV positron storage ring and a number of experimental photon beam lines utilizing synchrotron radiation. A number of radiological design considerations for such a facility need to be addressed. In addition to shielding considerations for each of the various components and the experimental beam lines, other issues involve production of radioactive and noxious gases, induced activity in the accelerator structures and other materials, potential radiation doses during abnormal occurrences, radiation fields produced by gas bremsstrahlung, and the off-site doses to the public. The methodology used to estimate the contributions from each of the above-mentioned issues is detailed. Estimates of the magnitude of the contribution of each component are presented, and doses, as well as released quantities, are compared to the relevant DOE and EPA requirements.

A Physically Based, Variable Contributing Area Model of Basin Hydrology / Un Modèle À Base Physique de Zone D'appel Variable de L'hydrologie Du Bassin Versant

Article

Mar 1979

A hydrological forecasting model is presented that attempts to combine the important distributed effects of channel network topology and dynamic contributing areas with the advantages of simple lumped parameter basin models. Quick response flow is predicted from a storage/contributing area relationship derived analytically from the topographic structure of a unit within a basin. Average soil water response is represented by a constant leakage infiltration store and an exponential subsurface water store. A simple non-linear routing procedure related to the link frequency distribution of the channel network completes the model and allows distinct basin sub-units, such as headwater and sideslope areas to be modelled separately. The model parameters are physically based in the sense that they may be determined directly by measurement and the model may be used at ungauged sites. Procedures for applying the model and tests with data from the Crimple Beck basin are described. Using only measured and estimated parameter values, without optimization, the model makes satisfactory predictions of basin response. The modular form of the model structure should allow application over a range of small and medium sized basins while retaining the possibility of including more complex model components when suitable data are available.

Removal of Artifact Depressions from Digital Elevation Models: Towards a Minimum Impact Approach

Article

Oct 2005
HYDROL PROCESS

Artifact depressions in digital elevation models (DEMs) interrupt flow paths and alter drainage directions. Techniques for removing depressions should enforce continuous flow paths in a way that requires the least modification of the DEM. Impacts on the spatial and statistical distributions of elevation and its derivatives were assessed for four methods of removing depressions: (1) filling; (2) breaching; (3) a combination of filling and breaching, with breaching constrained to a maximum of two grid cells; (4) a combination of filling and breaching based on an impact reduction approach (IRA). The IRA removes each depression using either filling or breaching, depending on which method has the least impact, in terms of the number of modified cells and the mean absolute difference in the DEM. Analysis of a LiDAR DEM of a landscape on the Canadian Shield showed significant differences in the impacts among the four depression removal methods. Depression filling, a removal method that is widely implemented in geographical information system software, was found to impact terrain attributes most severely. Constrained breaching, which relies heavily on filling for larger depressions, also performed poorly. Both depression breaching and the IRA impacted spatial and statistical distributions of terrain attributes less than depression filling and constrained breaching. The most sensitive landscapes to depression removal were those that contained large (i.e. >10%) flat areas, because of the occurrence of relatively large depressions in these areas. Copyright

The Ln(a/Tan-Beta) index—how to calculate it and how to use it within the TOPMODEL framework

Article

Feb 1995
HYDROL PROCESS

Topographic indices may be used to attempt to approximate the likely distribution of variable source areas within a catchment. One such index has been applied widely using the distribution function catchment model, TOPMODEL, of Beven and Kirkby (1979). Validation of the spatial predictions of TOPMODEL may be affected by the algorithm used to calculate the model's topographic index. A number of digital terrain analysis (DTA) methods are therefore described for use in calculating the TOPMODEL topographic index, In(a/tanβ) (a = upslope contributing area per unit contour; tanβ = local slope angle). The spatial pattern and statistical distribution of the index is shown to be substantially different for different calculation procedures and differing pixel resolutions. It is shown that an interaction between hillslope contributing area accumulation and the analytical definition of the channel network has a major influence on calculated In(a/tanβ) index patterns. A number of DTA tests were performed to explore this interaction. The tests suggested that an ‘optimum’ channel initiation threshold (CIT) may be identified for positioning river headwaters in a raster digital terrain model (DTM). This threshold was found to be dependent on DTM grid resolution. Grid resolution is also suggested to have implications for the validation of spatial model predictions, implying that ‘optimum’ TOPMODEL parameter sets may be unique to the grid scale used in their derivation. Combining existing DTA procedures with an identified CIT, a procedure is described to vary the directional diffusion of contributing area accumulation with distance from the channel network.

Digital Terrain Modeling: A review of hydrological, geomorphological, and biological applications

Article

Jan 1991
HYDROL PROCESS

The topography of a catchment has a major impact on the hydrological, geomorphological, and biological processes active in the landscape. The spatial distribution of topographic attributes can often be used as an indirect measure of the spatial variability of these processes and allows them to be mapped using relatively simple techniques. Many geographic information systems are being developed that store topographic information as the primary data for analysing water resource and biological problems. Furthermore, topography can be used to develop more physically realistic structures for hydrologic and water quality models that directly account for the impact of topography on the hydrology. Digital elevation models are the primary data used in the analysis of catchment topography. We describe elevation data sources, digital elevation model structures, and the analysis of digital elevation data for hydrological, geomorphological, and biological applications. Some hydrologic models that make use of digital representations of topography are also considered.

Quantitative Analysis of Land Surface Topography

Article

Jan 1987
EARTH SURF PROC LAND

Land surface topography significantly affects the processes of runoff and erosion. A system which determines slope, aspect, and curvature in both the down-slope and across-slope directions is developed for an altitude matrix. Also, the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix. A FORTRAN 66 program performs the analysis.

A network-indexbased version of TOPMODEL for use with high-resolution digital topographic data

Article

Jan 2004
HYDROL PROCESS

This paper describes the preliminary development of a network-index approach to modify and to extend the classic TOPMODEL. Application of the basic Beven and Kirkby form of TOPMODEL to high-resolution (2·0 m) laser altimetric data (based upon the UK Environment Agency's light detection and ranging (LIDAR) system) to a 13·8 km2 catchment in an upland environment identified many saturated areas that remained unconnected from the drainage network even during an extreme flood event. This is shown to be a particular problem with using high-resolution topographic data, especially over large appreciable areas. To deal with the hydrological consequences of disconnected areas, we present a simple network index modification in which saturated areas are only considered to contribute when the topographic index indicates continuous saturation through the length of a flow path to the point where the path becomes a stream. This is combined with an enhanced method for dealing with the problem of pits and hollows, which is shown to become more acute with higher resolution topographic data. The paper concludes by noting the implications of the research as presented for both methodological and substantive research that is currently under way. Copyright © 2004 John Wiley & Sons, Ltd.

Interpolation by Regularized Spline with Tension: II. Application to Terrain Modeling and Surface Geometry Analysis

Article

Aug 1993

A general approach to the computation of basic topographic parameters independent of the spatial distribution of given elevation data is developed. The approach is based on an interpolation function with regular first and second order derivatives and on application of basic principles of differential geometry. General equations for computation of profile, plan, and tangential curvatures are derived. A new algorithm for construction of slope curves is developed using a combined grid and vector approach. Resulting slope curves better fulfill the condition of orthogonality to contours than standard grid algorithms. Presented methods are applied to topographic analysis of a watershed in central Illinois.

Calculating Catchment Area with Divergent Flow Based on a Regular Grid

Article

Dec 1991
COMPUT GEOSCI-UK

T.Graham Freeman

A new procedure is described for determining the catchment areas for all cells in a regular elevation grid, a problem of fundamental importance in analyzing drainage patterns, mineral deposition, erosion, and pollution in streams and groundwater. The new procedure allows for divergent flow, which arises in most natural terrain on hill slopes. Failure to allow for this can introduce serious artifacts in the calculations. The procedure is demonstrated on analytic surfaces that give poor results if divergent flow is ignored, and is applied to natural terrain. Also discussed is the problem of clearing sinks or pits in the elevation model and flat spots.

Landform classification and soil distribution in hummocky terrain, Saskatchewan, Canada

Article

Oct 1987
GEODERMA

This study presents a classification of distinct, three-dimensional landform elements and examines the relationship between these landform elements and selected soil morphological properties of Udic Boroll soils in southern Saskatchewan, Canada. The classification is based on defined ranges of three criteria derived from topographic data: gradient, profile (downslope) curvature, and plan (across-slope) curvature. Seven landform elements are recognized: convergent shoulders, divergent shoulders, convergent backslopes, divergent backslopes, convergent footslopes, divergent footslopes, and level elements. All of the elements are easily identified in the field.The thicknesses of A horizons and depths to calcium carbonate of the soils were consistently greater in convergent versus divergent elements in the same profile group (e.g. shoulders), and showed an overall increase in the sequence shoulders<backslopes<level<footslope elements. Distinct groups of elements emerge from a statistical analysis of the differences between individual and bivariate means of soil morphological properties associated with each landform element. The differences in soil properties among the elements can be largely explained by differences in water movement and distribution in hillslope systems. The results of the study highlight the need to consider land-surface morphology during the development of research designs for soil related studies.

Prediction of soil properties by digital terrain modeling

Article

Dec 2002
ENVIRON MODELL SOFTW

We investigated two approaches for large-scale analysis and prediction of the spatial distribution of soil properties in an agricultural landscape in the Canadian prairies. The first approach was based on the implementation of nine types of digital terrain models (DTMs) and regression analysis of soil and topographic data. The second approach used a concept of accumulation, transit, and dissipation zones of the landsurface. Soil properties were soil moisture, residual phosphorus, solum thickness, depth to calcium carbonate, and organic carbon content. The dependence of soil properties on topography was supported by correlations for the upper soil layer. However, topographic control of soil moisture and residual phosphorus decreased with depth. Also, correlation coefficients and regression equations describing topographic control of soil moisture and residual phosphorus differed among seasons. This imposes limitations on regression-based predictions of the spatial distribution of soil properties. The prediction of soil property distribution with the concept of accumulation, transit and dissipation zones can be more successful and appropriate than the prediction based on linear regression. The variability in relationships between soil and topographic characteristics with depth may stem from spatial variability in the rate of decline of hydraulic conductivity with depth. Temporal variability in soil–topography relationships occurs because soil properties result from interactions of a variety of pedogenetic factors and processes marked by different temporal variability. In soil studies with digital terrain modelling, there is a need to take into account four types of variability in relations between soil and relief: regional, temporal, depth, and scale.

TAPES-G: A grid-based terrain analysis program for the environmental sciences

Article

Aug 1996
COMPUT GEOSCI-UK

TAPES-G is a grid-based terrain analysis program that computes slope, aspect, upslope contributing area, profile and plan curvature and several other topographic attributes for each cell of a square-grid digital elevation model (DEM). These topographic attributes can be used to represent key physical processes in a form simple enough to allow modeling at catchment and larger scales. The program creates initially a depressionless DEM if desired. Upslope contributing area can be calculated using either the classical D8 algorithm, the quasi-random Rho8 algorithm, the multiple flow direction FD8/FRho8 algorithm or Costa-Cabral and Burges's stream tube-based DEMON algorithm. Stream networks, sub-catchments and the spatial distribution of individual attributes can be plotted interactively or copied to the ARC/INFO geographic information system (GIS) for further processing.

The Extraction of Drainage Networks From Digital Elevation Data

Article

Aug 1984
Comput Vis Graph Image Process

The extraction of drainage networks from digital elevation data is important for quantitative studies in geomorphology and hydrology. A method is presented for extracting drainage networks from gridded elevation data. The method handles artificial pits introduced by data collection systems and extracts only the major drainage paths. Its performance appears to be consistent with the visual interpretation of drainage patterns from elevation contours.

Geomorphometry—Diversity in Quantitative Surface Analysis

Article

Mar 2000

Richard J. Pike

A widening variety of applications is diversifying geomorphometry (digital terrain modelling), the quantitative study of topography. An amalgam of earth science, mathematics, engineering and computer science, the discipline has been revolutionized by the computer manipulation of gridded terrain heights, or digital elevation models (DEMs). Its rapid expansion continues. This article reviews the remarkable diversity of recent morphometric work in 15 selected topics and discusses their significance and prospects. The quantitative analysis of industrial microsurface topography is introduced to the earth science community. The 14 other topics are Internet access to geomorphometry; global DEMs; DEM modelling of channel networks; self-organized criticality; fractal and wavelet analysis; soil resources; landslide hazards; barchan dunes; harvesting wind energy; sea-ice surfaces; sea-floor abyssal hills; Japanese work in morphometry; and the emerging fields of landscape ecology and image understanding. Closing remarks note reasons for the diversity within geomorphometry, speculate on future trends and recommend creating a unified field of surface representation.

A Physically Based, Variable Contributing Area Model of Basin Hydrology

Article

Mar 1979

A hydrological forecasting model is presented that combines the important distributed effects of channel network topology and dynamic contributing areas with the advantages of simple lumped parameter basin models. Quick response flow is predicted from a storage/contributing area relationship derived analytically from the topographic structure of a unit within a basin. Average soil water response is represented by a constant leakage infiltration store and an exponential subsurface water store. A simple non-linear routing procedure related to the link frequency distribution of the channel network completes the model and allows distinct basin sub-units, such as headwater and sideslope areas to be modeled separately. Procedures for applying the model and tests with data from the Crimple Beck basin in the United Kingdom are described.

A New Method For The Determination Of Flow Directions And Upslope Areas In Grid Digital Elevation Models

Article

Dec 2001

David G. Tarboton

A new procedure for the representation of flow directions and calculation of upslope areas using rectangular grid digital elevation models is presented. The procedure is based on representing flow direction as a single angle taken as the steepest downwards slope on the eight triangular facets centered at each grid point. Upslope area is then calculated by proportioning flow between two downslope pixels according to how close this flow direction is to the direct angle to the downslope pixel. This procedure offers improvements over prior procedures that have restricted flow to eight possible directions (introducing grid bias) or proportioned flow according to slope (introducing unrealistic dispersion). The new procedure is more robust than prior procedures based on fitting local planes while retaining a simple grid based structure. Detailed algorithms are presented and results are demonstrated through test examples and application to digital elevation data sets.

Higher isn't Necessarily Better: Visibility Algorithms and Experiments

Article

Jul 1998

We describe several fast programs to compute viewsheds and weighted visibility indices for observation points in a raster terrain. These programs explore various tradeoffs between speed and accuracy. We have analyzed many cells of data; there is no strong correlation between a point's elevation and its weighted visibility index. However, the, very few, high visibility points tend to characterize features of the terrain. This work can form a basis for automatically locating observers jointly to cover a terrain region of interest. Keywords: visibility, viewshed, line-of-sight. 1 Introduction Visibility research, calculating lines-of-sight and viewsheds, on terrain databases, is an established, and important, field in GIS. Nevertheless, progress is still possible, since both more powerful Unix workstation hardware, with tens of megabytes of memory and software environments, and 1 much larger amounts of input data are available. The research reported here would not have been fea...

A physically based model for calculating contributing area on hillslopes and along valley bottoms Coping with topographic depression in digital terrain analysis Removal of artifact depressions from DEMs: towards a minimum impact approach

1123-1130

J B Lindsay Lindsay Jb
Creed

Lindsay JB, 2003. A physically based model for calculating contributing area on hillslopes and along valley bottoms. Water Resources Research 39(12): 1332. DOI: 10·1029/2003WR002576. Lindsay JB, 2004. Coping with topographic depression in digital terrain analysis. PhD thesis, University of Western Ontario. Copyright  2005 John Wiley & Sons, Ltd. 1129 Hydrol. Process. 19, 1123–1130 (2005) J. B. LINDSAY Lindsay JB, Creed IF, 2005. Removal of artifact depressions from DEMs: towards a minimum impact approach. Hydrological Processes 19: in press.

Coping with topographic depression in digital terrain analysis

Jan 2004

Jb Lindsay

Lindsay JB, 2004. Coping with topographic depression in digital terrain analysis. PhD thesis, University of Western Ontario.

Digitales Gelände-Modell (DiGeM) Terrain Analysis Software

Aug 2002

O Conrad

Conrad O, 2002. Digitales Gelände-Modell (DiGeM) Terrain Analysis Software. http://www.geogr.uni-goettingen.de/pg/saga/ digem/ (15 August 2004).

The Terrain Analysis System: A tool for hydro-geomorphic applications

Abstract

No full-text available

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