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FLOOD HAZARD MAPPING OF RIVER BASINS IN CARAGA REGION, MINDANAO, PHILIPPINES THROUGH THE CSU PHIL-LIDAR 1 PROJECT

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In this paper, we share our activities and recent accomplishments in utilizing high spatial resolution Light Detection and Ranging (LiDAR) datasets and other geospatial datasets and techniques for flood hazard mapping of river basins in Caraga Region, Mindanao, Philippines through the CSU Phil-LiDAR 1 project. CSU Phil-LiDAR 1 is one of several projects under the " Phil-LiDAR1: Hazard Mapping of the Philippines using LiDAR " program initiated and supported by the Department of Science and Technology (DOST). Projects under this program are being implemented nationwide by fifteen (15) higher education institutions (HEIs) for 3 years starting 2014. An extension of the University of the Philippines' Disaster Risk Exposure Assessment for Mitigation (DREAM) program, Phil-LIDAR 1′s purpose is for HEIs to utilize LiDAR datasets to generate flood hazard maps of their assigned project areas which are distributed throughout the Philippines. CSU Phil-LiDAR 1 in particular aims to derive Digital Surface Models (DSMs) and Digital Terrain Models (DTMs) from preprocessed LiDAR data, and to utilize these elevation datasets, together with data gathered from field surveys (cross-sections, bathymetry and hydrology) as inputs in the development of flood models. The flood models are then used to generate flood hazard maps of the river basins and watersheds of Caraga Region. Two of the major outputs of the projects during the first two years of its implementation are 1-m resolution LiDAR DTMs and DSMs of the project areas. From these datasets, we were able to generate a risk exposure database consisting of buildings, roads, bridges and other structures. More importantly, we were able to develop flood models and generate detailed flood hazard maps. The said models were also used to reconstruct recent flooding events in the project areas. Other project outputs include near-real time flood extent mapping and water level forecasting which are useful for flood disaster preparedness, prevention and response.
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FLOOD HAZARD MAPPING OF RIVER BASINS IN CARAGA REGION, MINDANAO,
PHILIPPINES THROUGH THE CSU PHIL-LIDAR 1 PROJECT
Meriam Makinano-Santillan and Jojene R. Santillan
CSU Phil-LiDAR 1, Caraga Center for Geoinformatics, Caraga State University
Ampayon, Butuan City 8600 Philippines
Email: Email: meriam.makinano@gmail.com
KEY WORDS: LiDAR, flood hazard mapping, Caraga Region, Mindanao, Philippines
ABSTRACT: In this paper, we share our activities and recent accomplishments in utilizing high spatial resolution
Light Detection and Ranging (LiDAR) datasets and other geospatial datasets and techniques for flood hazard mapping
of river basins in Caraga Region, Mindanao, Philippines through the CSU Phil-LiDAR 1 project. CSU Phil-LiDAR 1
is one of several projects under the Phil-LiDAR1: Hazard Mapping of the Philippines using LiDAR program
initiated and supported by the Department of Science and Technology (DOST). Projects under this program are being
implemented nationwide by fifteen (15) higher education institutions (HEIs) for 3 years starting 2014. An extension
of the University of the Philippines Disaster Risk Exposure Assessment for Mitigation (DREAM) program,
Phil-LIDAR 1s purpose is for HEIs to utilize LiDAR datasets to generate flood hazard maps of their assigned project
areas which are distributed throughout the Philippines. CSU Phil-LiDAR 1 in particular aims to derive Digital Surface
Models (DSMs) and Digital Terrain Models (DTMs) from preprocessed LiDAR data, and to utilize these elevation
datasets, together with data gathered from field surveys (cross-sections, bathymetry and hydrology) as inputs in the
development of flood models. The flood models are then used to generate flood hazard maps of the river basins and
watersheds of Caraga Region. Two of the major outputs of the projects during the first two years of its implementation
are 1-m resolution LiDAR DTMs and DSMs of the project areas. From these datasets, we were able to generate a risk
exposure database consisting of buildings, roads, bridges and other structures. More importantly, we were able to
develop flood models and generate detailed flood hazard maps. The said models were also used to reconstruct recent
flooding events in the project areas. Other project outputs include near-real time flood extent mapping and water level
forecasting which are useful for flood disaster preparedness, prevention and response.
1. INTRODUCTION
1.1 Background
Tropical storms passing through the Philippines have resulted in widespread flooding, deaths and destruction across
the country. In Mindanao, heavy rains brought by Sendong, Agaton and Seniang caused rivers to overflow in the
cities of Cagayan de Oro, Iligan and Butuan. Many houses have been submerged, properties destroyed, and human
lives taken by rampaging waters from the overflowing rivers. What happened during Sendong, Agaton and Seniang
may be just examples of what are yet to come. There is an urgent need to prepare ourselves for forthcoming flood
disasters as storms and heavy rains continue to be fiercer in recent years.
The CSU Phil-LiDAR 1 project is a three-year project currently implemented by the College of Engineering &
Information Technology of the Caraga State University in Ampayon, Butuan City, Mindanao, Philippines. It is one of
several projects under the “Phil-LiDAR-1. Hazard Mapping of the Philippines using LiDAR” program funded by the
Department of Science and Technology (DOST). The Phil-LiDAR 1 Program aims to produce detailed flood hazard
maps for the 2/3 of the Philippine river systems using LiDAR Technology. The program serves as an urgent response
to the echoing need to better prepare the country and its people for natural disasters such as flooding. The program is
an expansion of the Disaster Risk and Exposure Assessment for Mitigation (DREAM) Program formed in 2011 and
implemented by the University of the Philippines Diliman. Projects under Phil-LiDAR 1 program are being
implemented nationwide since 2014 by several higher education institutions (HEIs). CSU Phil-LiDAR 1 in particular
will generate flood hazard maps of the river basins of Caraga Region (except the Agusan River Basin which has been
covered by the UP DREAM program).
1.2 Project Objectives
Taking advantage of LiDAR technology, the project aims to generate flood hazard maps that can be used to determine
at the household level those houses and structures that are at risk of an impending flood disaster.
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Generally, a hazard map for a specific flooding event or scenario would contain:
the expected inundation level and flooding extent categorized into low, medium and high hazards;
locations of structures (such as households, schools, commercial buildings, roads, bridges, land cover types,
and evacuation centers, among others);
political boundaries (provincial, city/municipal, and barangay); and
information about the flooding event where the map is applicable (e.g., according to volume and intensity of
rainfall).
Depending on how much rain has fallen in the past number of hours, flood hazard maps can tell us if our house, the
houses of our relatives, a nearby road, our rice fields, etc. will be flooded in the next number of hours. Because of the
advance information that flood hazard maps provide, there is an adequate time for us to prepare ourselves, secure our
properties, and to evacuate, if necessary. It also helps local government agencies for localized emergency response
(i.e. evacuation and access routes, road closures, selection of sites for key rescue facilities).
1.3 Areas Covered by the Project
For three years starting 2014, the project
will cover twelve (12) river basins within
Caraga Region (Figure 1 and Table 1),
with a total drainage area of
approximately 4,750 square kilometers.
These river basins have been prioritized
according to the severity of recent flood
disasters (for example during Agaton and
Seniang). For each river basin, the CSU
Phil-LIDAR 1 project will generate: i.)
LiDAR data products such as DTMs and
DSMs; ii.) hazard exposure database
derived from LiDAR data products; iii.)
flood models; and iv.) flood hazard maps.
Table 1. List of river basins of Caraga
Region covered by the CSU Phil-LiDAR
1 project.
2. FLOOD HAZARD MAPPING
OVERVIEW
The series of steps to generate flood hazard maps are illustrated in Error! Reference source not found.. First,
information about the volume and intensity of rainfall is obtained. This information is then fed into a mathematical
simulation model (or flood model) to compute how much volume of runoff or flood water is generated in the
mountains when it rains, and to determine how this flood water flows downwards into the rivers and overflows into
the floodplains. In order for the flood model to work, it would require the following information: 1) topography; 2)
geometry of the river; 3) location of man-made structures; and 4) the types of land-cover. This information will be
used by the model to compute the volume of flood water, determine the speed and direction of the flow, and finally
determine the depth and extent of inundation. From the computed depth and inundation extent, a flood hazard map is
Year 1
(2014)
Year 2
(2015)
Year 3 (2015
Cabadbaran
Tandag
Surigao
Mainit-
Tubay
Hubo-
Otieza
Magallanes
Tago
Hinatuan
Cantilan
Bislig
Malinao
Inlet 1
GaasLulet
(Malinao
Inlet 2)
Figure 1. Map showing the river basins covered by the project.
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then prepared. For it to be useful, flood hazard maps must be detailed in such way that it is possible to locate the areas
at risk of flooding at the household level. It must also be accurate to ensure that the flood inundation and extent
depicted in the map is as near as possible to what is occurring or what will occur in the ground.
3. LIDAR DATA AS INPUT IN FLOOD HAZARD MAPPING
The accuracy and detail of information depicted in a flood hazard map is
dependent on the topographic data used during flood modelling. In the
generation of flood hazard maps, the CSU Phil-Lidar 1 project utilizes
topographic information extracted from LiDAR data acquired by the
University of the Philippines Phil-Lidar 1 Data Acquisition Component.
LiDAR or “Light Detection and Ranging” is a remote sensing method that
uses light in the form of a pulsed laser to measure ranges (variable distances)
to the Earth from the sensor. These light pulsescombined with other data
recorded by the airborne system generate precise, three-dimensional (3D)
information about the shape of the Earth and its surface characteristics.
Among many things, it is useful for such tasks as surface mapping,
vegetation mapping, transportation corridor mapping, transmission route
mapping, and 3-D building mapping.
LiDAR data provide the much-needed accuracy and topographic detail to
model and delineate the potential extent of flooding due to the high accuracy
of the data and the ability to resolve small features that influence flow paths.
There are two LiDAR data products that are especially used in detailed flood
hazard mapping: 1) Digital Surface Model (DSM) and 2) Digital Terrain
Model (Figure 3). DTM and DSM are generally referred to as Digital
Elevation Models (DEM). A DSM is a representation of the earth’s surface
where all features including all man-made structures and vegetation are
present. When these features are removed from the DSM, it will result to a DTM which is also called a “bare earth”
DEM. Both the DTM and DSM provide topographical and surface feature information needed by the flood model in
its computation of how much rainwater drains into the river and how much will overflows, and how this overflow will
Figure 2. Process flow of generating flood hazard maps.
Figure 3. Examples of DSM and
DTM of an area.
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cause flooding in a certain locality. Because the underlying topography is finely represented by the LiDAR DTM, the
flood model is fed with the right information to adequately account for the differences in elevation of the locality and
this allow the model to determine which areas the flood water will flow and as to what extent it will flow through
time.
4. GENERATING FLOOD HAZARD MAPS OF CARAGA REGION RIVER BASINS
Within the CSU Phil-LiDAR 1 project, the steps involved in flood hazard map generation were streamlined into 3
major activities namely, field surveying, LiDAR data processing, and flood modelling.
4.1 Field Surveying
All field data collection activities of the project are
being handled by the Field Survey Team (FST).
Gathering information from the field ensures that
the actual characteristics of the rivers and its
floodplains are captured. Knowing how much rain
falls into the watershed, how wide and deep the
river is, how fast the water flows, and how much
water flows along the river would allow us to
determine the capacity of the river and what levels
it would take for the river to overflow. To gather all
this information, the FST conducts river
cross-section surveys through the use of Geodetic
Engineering techniques and high precision
instruments, and flow measurements through
installation of rain gauges, water level sensors, and
velocity meters
4.2 The Data Processing Team
LiDAR datasets of the rivers
systems covered by the project
are being processed by the Data
Processing Team (DPT) to
generate DTMs and DSMs. All
LiDAR data used by the project
are being collected by the
Phil-LiDAR 1 Data Acquisition
Component of the University of
the Philippines Diliman. These
datasets were pre-processed by
the Phil-LiDAR 1 Data Pre-Processing Component (DPPC) before Validation and river bathymetry data gathered and
provided to the project by Phil-LIDAR 1 Data Validation and Bathymetry Component of the UP Diliman are also
processed by the DPT to assess accuracy of the LiDAR products and to incorporate river bed data into the DTMs. The
DPT also extracts from the DSMs features such as houses, buildings, roads and bridges that will be utilized for
mapping structures at risk to flooding.
4.3 The Flood Modeling Team
The Flood Modeling Team (FMT) uses computer models to predict flooding due to rainfall of varying volume and
intensity. The FMT uses the DTM and information extracted from the DSM during the flood modeling process. The
main outputs of the FMT are flood models and flood hazard maps.
The flood simulation software/programs used are the Hydrologic Engineering Center Hydrologic Modelling System
(HEC HMS) version 3.5 and HEC River Analysis System (HEC RAS) version 4.1. Various geospatial datasets were
utilized in the development of flood simulation models. In HEC HMS model development, a 10-m Synthetic
Figure 4. Some of the pictures of the fieldwork activities of
the Field Survey Team (FST).
Figure 5. Examples of LiDAR dataset being processed by the Data Processing
Team (DPT).
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Aperture Radar (SAR) Digital Elevation Model (DEM) was used for sub-basin delineations and for derivation of
topography-related parameters of the model such as slope and elevation. Images acquired by the Landsat 8 satellite
were also utilized to derive a landcover map using Maximum Likelihood classification. The landcover map is
necessary for the derivation of land-cover-related model parameters such as surface roughness coefficient, and
runoff/infiltration capacities. River width and cross-section data obtained from field surveys as well as those
extracted from 1-m resolution LiDAR-derived Digital Terrain Model (DTM) were also used to estimate the channel
routing parameters of the model. For HEC RAS model development, river bed topography (obtained from
bathymetric surveys), sea bed topography (obtained from a NAMRIA topographic map), LiDAR DTM, building
footprints (with top elevation) extracted from LiDAR DSM, and the same landcover map derived from Landsat 8 OLI
satellite image were used as major inputs.
The HEC HMS-based hydrologic model computes for the volume of water coming from the upstream watersheds
caused by rain falling in these areas. Rainfall depths recorded by rain gauges within and in the vicinity of the river
basin are being used as input into the HEC HMS to compute discharge hydrographs for specific locations in the river
basin, specifically at those locations where the upstream watersheds ends and the floodplain portions begin. The
discharge hydrographs depict the volume of water per unit time (in m3/s) that drains into the main river at these
locations. These hydrographs are then used as inputs into the HEC RAS hydraulic model to generate the flood depth
and hazard maps. HEC RAS is a one-dimensional flood model that utilizes river and flood plain geometric data (from
topographic and hydrographic surveys and LiDAR Digital Terrain Model - DTM), land-cover and surface roughness
(from remotely-sensed images), and discharge hydrographs in order to compute water levels all throughout the river.
Once these water levels are computed, the flooded or inundated areas along the river and in the floodplains are
estimated by intersecting the water surface profiles into a high resolution LiDAR DTM.
For each river basin, the project will generate flood hazard maps representing actual flood events and hypothetical
flooding events. The actual flood events represent maximum flood level and extent caused by heavy to torrential rains
brought by Tropical Storms Agaton and Seniang. The rainfall data used in the flood simulations those recorded by
rain gauges installed by the Advanced Science and Technology Institute DOST. On the other hand, the hypothetical
flooding events represent maximum flood levels and extent caused by rainfall events with varying intensity and
duration (i.e., varying return periods). The rain return periods considered are 2-, 5-, 10-, 25-, 50-, 100-year. Rainfall
Intensity Duration Frequency (RIDF) curves generated by Philippine Atmospheric, Geophysical and Astronomical
Services (PAGASA) for various locations in Caraga Region were utilized as inputs in the flood simulation.
The FMT incorporates all the
information from the field
surveys to assess whether the
flood hazard maps generated are
realistic and accurate or not. The
flow measurement datasets are
being used to calibrate and
validate the upstream
hydrological model to ensure
that its computations of flow
during rainfall events are
accurate within acceptable levels
of accuracy. The FMT together
with the FST also conducts
validation surveys to check the
accuracy of the flood hazard
maps. The teams visit random
locations within a river basin and
interview the nearest household
about the occurrence of flooding
in their locality. Information gathered during the surveys are the geographic locations of the households, the
maximum depth of flood, the estimated dates when the flooding occurred, and the causes of flooding (i.e. if it was due
to overflowing of the river or an accumulation of rainwater).
Figure 6. Some of the pictures of the FMT together with the FST during the conduct
of flood validation surveys.
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5. RECENT ACCOMPLISHMENTS
5.1 LiDAR DTM and DSM Generation and Feature Extraction
As of writing, the CSU Phil-LiDAR 1 project has completed generating DTMs and DSMs covering a total of
5,684.80 km2 out of the 8,167.55 km2 pre-processed LiDAR data provided to the project. This is in cooperation with
the UP Diliman DREAM/Phil-LiDAR 1 Data Pre-Processing Component (DDPC). This data covers eight (8) out of
the twelve (12) river basins assigned to Caraga State University. In terms of feature extraction and attribution (i.e.
digitizing the different structures and naming the type of structure such as residential, commercial, etc.), the CSU
Phil-LiDAR 1 project has completed the five (5) out of the twelve (12) river basins. There are a total number of
54,974 features extracted and attributed. Figure 7 shows a sample processed LiDAR data with the corresponding
extracted features.
Figure 7. Sample processed LiDAR data and extracted features (Cabadbaran river basin).
5.2 Flood Models Developed
In terms of flood model development, the CSU Phil-LiDAR 1 has completed the development and calibration of the
HMS models of four river basins: Cabadbaran, Mainit-Tubay, Tago and Tandag. Figure 8 and Figure 9 show the
interfaces of the HMS models developed and results of the model calibration, respectively. Using model performance
evaluation measures, the HEC HMS models’ performance ranges from “good” to “very satisfactory” in simulating
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36th Asian Conference on Remote Sensing 2015 (ACRS 2015), Quezon City, Philippines, Volume 1, pp. 599-610, 2015
discharge hydrographs when compared with measured hydrographs. In terms of HEC RAS model development, the
project completed the models of Cabadbaran and Mainit-Tubay river basins. Figure 10 and Figure 11 shows the
interfaces of the HEC RAS models developed for the two river basins.
Figure 8. Interfaces of the HMS models developed (UR: Cabadbaran river basin; UL: Mainit-Tubay river basin; LL:
Tago river basin; LR: Tandag river basin)
Figure 9. Results of the HEC HMS model calibrations.
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Figure 10. Interface of the developed HEC RAS model of Cabadbaran river basin.
Figure 11. Interface of the developed HEC RAS model of Mainit-Tubay river basin
5.3 Flood Hazard Maps
So far we have generated flood hazard maps for three out of the 12 river basins in Caraga Region. These river basins
are Cabadbaran, Mainit-Tubay and Tago. For each river basin we generated 6 sets flood hazard maps consisting of the
following flood events: Agaton, Seniang, 2-year, 5-year, 10-year, 25-year, 50-year, and 100-year rain return periods.
These maps have spatial resolutions of 1 x 1 m. Examples of these flood hazard maps for the Cabadbaran and
Mainit-Tubay River Basins for the Agaton flood event are shown in Figure 12 and Figure 13.
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36th Asian Conference on Remote Sensing 2015 (ACRS 2015), Quezon City, Philippines, Volume 1, pp. 599-610, 2015
Figure 12. Flood hazard map of Cabadbaran river basin during typhoon “Agaton” Figure 13. Flood hazard map of Mainit-Tubay river basin during typhoon “Agaton”
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5.4 Accuracy of Flood Hazard Maps
Figure 14 and 15 show maps of the validation points used to assess the accuracy of flood hazards generated for the
Agaton flood events for the Mainit-Tubay and Tago River Basins. Due to space constraints the maps of validation
points collected for Cabadbaran River Basin (Agaton event), and the maps of validations points collected to assess the
accuracy of the Seniang event flood hazard maps of the three river basins are not shown. The overall accuracy of the
flood hazard maps generated by the project ranges from 62-70% at least for the hazard maps generated for the Agaton
flood event (Tables 2-4).
Figure 14. Map showing the validation points used to assess the accuracy of the Mainit-Tubay river basin flood hazard
map during the typhoon “Agaton”
Table 2. Results of accuracy assessment of the Mainit-Tubay River Basin flood hazard map for the Agaton event.
Actual Flooding Scenario
User's Accuracy (%)
Flooded
Not Flooded
Total
Flood Model Simulated
Flooding Scenario
Flooded
17
29
46
37
Not Flooded
24
97
121
80
Total
41
126
167
Producer's Accuracy (%)
41
77
Sum of Diagonal Values
114
Overall Accuracy (%)
68
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36th Asian Conference on Remote Sensing 2015 (ACRS 2015), Quezon City, Philippines, Volume 1, pp. 599-610, 2015
Figure 15. Map showing the validation points used to assess the accuracy of the Tago river basin flood hazard map
during the typhoon “Agaton”
Table 3. Results of accuracy assessment of the Tago River Basin flood hazard map for the Agaton event.
Actual Flooding Scenario
User's Accuracy (%)
Flooded
Not Flooded
Total
Flood Model Simulated
Flooding Scenario
Flooded
57
7
64
89
Not Flooded
23
14
37
38
Total
80
21
101
Producer's Accuracy (%)
71
67
Sum of Diagonal Values
71
Overall Accuracy (%)
70
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36th Asian Conference on Remote Sensing 2015 (ACRS 2015), Quezon City, Philippines, Volume 1, pp. 599-610, 2015
Table 4. Results of accuracy assessment of the Cabadbaran River Basin flood hazard map for the Agaton event.
Actual Flooding Scenario
User's Accuracy (%)
Flooded
Not Flooded
Total
Flood Model Simulated
Flooding Scenario
Flooded
19
14
33
58
Not Flooded
24
42
66
64
Total
43
56
99
Producer's Accuracy (%)
44
75
Sum of Diagonal Values
61
Overall Accuracy (%)
62
6. OTHER PROJECT OUTPUTS
In addition to the flood hazard maps, the project also developed a water level forecasting system that can generate
forecasts on how water level in a specific section of a river will change through time based on rainfall events that have
previously occurred. These forecasts, which are updated every 10 minutes, can be viewed in the project website at
http://carsulidar1.wordpress.com/.
Another major output developed by the project is an online geo-visualization application called "Web-based
Near-real Time Flood Event Visualization and Damage Estimations" or Flood EViDEns (public version available at
http://121.97.192.11:8082). The application is targeted to be utilized by the Local Government Units (LGUs) and
communities in the Caraga Region, Mindanao, Philippines to assist them in geospatially informed decision making in
times of flood disasters. The application is an amalgamation of web mapping technology, various geospatial datasets
including LiDAR-derived elevation and information products, hydro-meteorological data, and flood simulation
models to visualize in near-real time the current and possible future extent of flooding and its associated damages to
infrastructures. The Flood EViDEns application facilitates the release and utilization of this near-real time
flood-related information through a user-friendly front end interface consisting of web map, tables and charts. The
information provided by Flood EViDEns is very important especially to the LGUs and the community as it can
increase awareness and responsiveness of the public to the impending flood disaster. Providing this kind of
information during a heavy rainfall event is useful as it could assist in preparation for evacuation, in easily identifying
areas that need immediate action, in identifying areas that should be avoided, and in estimating the severity of damage
to people and infrastructure as flooding progresses
7. CONCLUDING REMARKS
Informed decision making before, during and after a flood disaster is what the CSU Phil-LIDAR 1 project wants to
achieve. With the generation of flood hazard maps and various tools and applications, the project can make proper
information available to guide disaster managers and the Caraga Region communities to better prepare for onslaught
of impending and potential flood hazards.
ACKNOWLEDGEMENT
This research is conducted by the Caraga State University in collaboration with the University of the Philippines
Diliman. This research is an output of the “Phil-LiDAR 1: Nationwide Hazard Mapping of the Philippines Using
LiDAR: Caraga Region” project. We are grateful to the Department of Science and Technology (DOST) for the
financial support. We also thank all CSU-Phil-LIDAR 1 technical staff and assistants, as well as the LGUs in the
project areas for their contributions and assistance extended to the project.
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We discuss in this paper the development, including the features and functionalities, of an open source web-based flood hazard information dissemination and analytical system called “Flood EViDEns”. Flood EViDEns is short for “Flood Event Visualization and Damage Estimations”, an application that was developed by the Caraga State University to address the needs of local disaster managers in the Caraga Region in Mindanao, Philippines in accessing timely and relevant flood hazard information before, during and after the occurrence of flood disasters at the community (i.e., barangay and household) level. The web application made use of various free/open source web mapping and visualization technologies (GeoServer, GeoDjango, OpenLayers, Bootstrap), various geospatial datasets including LiDAR-derived elevation and information products, hydro-meteorological data, and flood simulation models to visualize various scenarios of flooding and its associated damages to infrastructures. The Flood EViDEns application facilitates the release and utilization of this flood-related information through a user-friendly front end interface consisting of web map and tables. A public version of the application can be accessed at http://121.97.192.11:8082/. The application is currently expanded to cover additional sites in Mindanao, Philippines through the “Geo-informatics for the Systematic Assessment of Flood Effects and Risks for a Resilient Mindanao” or the “Geo-SAFER Mindanao” Program.
Conference Paper
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Rainfall has always been a factor in every flood occurrences in most, if not all, of the floodplain areas of Caraga Region, Mindanao, Philippines. Apart from its intensity, another parameter that has significant value in assessing flood incidents is the depth and velocity of the flood water. Flooding is the underlying phenomenon that the Phil-LiDAR 1 Project of Caraga State University initiated the development of an interactive web-mapping application that may be used as a tool for flood preparedness. The application was devised as one of many ways to assist the communities and Local Government Units of Caraga Region in making a sound and efficient decision in preventing and alleviating flood risks. The application requires the user to specify parameters, like municipality, barangay, amount of rainfall and to draw a polygon or point on the Web map interface, which will serve as the basis in forecasting flood risks. The application will basically provide flood information such as flood depth, flood duration and recession time and the time interval the flood water reaches the polygon or point drawn. It can also suggest safe route to the nearest evacuation shelter. Map displays and map features were built using the Openlayers API, while the extraction of data, and the flood extent calculations and analysis were JavaScript " s. Scripts retrieve the data from PostgreSQL spatial database and eventually display the tabulated information.
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