Jeff Smithers

Jeff Smithers
University of KwaZulu-Natal | ukzn · School of Engineering

PhD

About

59
Publications
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983
Citations

Publications

Publications (59)
Article
It is widely accepted that urban development results in larger flood peak discharges with faster catchment response times, larger total runoff volumes and lower base flow volumes. However, these effects have not previously been studied in the context of the specific characteristics of fast-growing urban areas in developing countries, which are gene...
Article
Full-text available
Frequency analysis of extreme rainfall and flood events are used to determine design rainfalls and design floods which are needed to design hydraulic structures such as dams, spillways and culverts. Standard methods for frequency analysis of extreme events are based on the assumption of a stationary climate. However, this assumption in rainfall and...
Article
Full-text available
Study region South Africa Study focus The Probable Maximum Precipitation (PMP) is the theoretical upper limit of extreme rainfall and is widely used by engineers and hydrologists to determine the Probable Maximum Flood (PMF) which is critical for the design and risk management of high-hazard hydraulic structures. In South Africa, the PMP was last...
Technical Report
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Final report for WRC project on design flood estimation in urban areas in South Africa
Article
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The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified ag...
Article
Full-text available
The estimation of design rainfalls is necessary to estimate the exceedance probabilities of extreme floods required to design hydraulic structures and to quantify the risk of failure of these structures. New approaches to estimating extreme rainfall events are being developed internationally. This paper reviews methods for estimating design rainfal...
Article
Run-off is dependent on interactions between rainfall intensity, antecedent soil moisture conditions and land cover while peak discharge from a catchment is closely related to the run-off volume generated. Both run-off volume and peak discharge are drivers to sediment yield. The purpose of this study was to increase understanding of run-off and soi...
Article
Full-text available
This paper contains a critical review of the norms employed in the design of soil and water conservation structures in the South African sugar industry and highlights research needs in order to update them. Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable...
Article
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A number of severe flooding events have occurred both in South Africa and internationally in recent years. Furthermore, changes in both the intensity and frequency of extreme rainfall events have been documented, both locally and internationally, associated with climate change. The recent loss of life, destruction of infrastructure, and associated...
Article
Full-text available
In engineering and flood hydrology, the estimation of a design flood associates the magnitude of a flood with a level of exceedance, or return period, for a given site. The use of a regional flood frequency analysis (RFFA) approach improves the accuracy and reliability of estimates of design floods. However, no RFFA method is currently widely used...
Article
Full-text available
Design flood estimation (DFE) is essential in the planning and design of hydraulic structures. In South Africa, outdated methods are widely applied for DFE. In this paper the potential of a continuous simulation modelling (CSM) approach to DFE in South Africa, using the daily time-step ACRU agrohydrological model, is investigated. The paper focuses...
Conference Paper
Full-text available
South Africa currently has no set guidelines for Design Flood Estimation (DFE). However, there are several manuals which provide designers with several recommended methods. Many of these methods were developed in the late 1970s and need to be updated and modernized. Flood Frequency Analysis (FFA) can be performed at-site or at a regional scale usi...
Article
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This study has been undertaken to establish the probable causes of the almost 4 m drop in the level of Lake Sibhayi between 2001 and 2014, to assess the impact of abstractions for domestic water consumption and by commercial plantations on lake levels, and to determine what sustainable yield can be abstracted from Lake Sibhayi. From the analysis an...
Article
In single-event deterministic design flood estimation methods, estimates of the peak discharge are based on a single, representative catchment response time parameter. In small catchments, a simplified convolution process between a single observed hyetograph and hydrograph is generally used to estimate time parameters such as the time to peak (TP),...
Article
The environmental footprint of agricultural production can vary significantly both between countries and within a country based on regional conditions and agricultural practices. A life cycle assessment approach was used to model fossil fuel energy inputs and greenhouse gas emissions associated with the production of sugarcane in South Africa. Resu...
Article
Despite uncertainties and errors in measurement, observed peak discharges are the best estimate of the true peak discharge from a catchment. However, in ungauged catchments, the catchment response time is a fundamental input to all methods of estimating peak discharges; hence, errors in estimated catchment response time directly impact on estimated...
Article
Full-text available
Catchment response time parameters are one of the primary inputs required when design floods, especially in ungauged catchments, need to be estimated. The time of concentration (TC) is the most frequently used time parameter in flood hydrology practice, and continues to find application in both event-based methods and continuous hydrological models...
Article
Large errors in estimates of peak discharge in medium to large catchments in South Africa can be largely ascribed to significant errors in the estimation of the catchment response time, mainly as a consequence of the use of inappropriate time variables, the inadequate use of a simplified convolution process between rainfall-runoff time variables, a...
Article
Full-text available
Estimates of design floods are required for the design of hydraulic structures and to quantify the risk of failure of the structures. Many international studies have shown that design floods estimated using a regionalised method result in more reliable estimates of design floods than values computed from a single site or from other methods. A numbe...
Article
Full-text available
Design point rainfall estimates assume a uniform distribution of rainfall over a catchment, and hence are only representative for a limited area. For larger areas, areal reduction factors (ARFs) are used to convert design point rainfall depths/intensities to an average areal design rainfall depth/intensity for a catchment-specific critical storm du...
Article
Full-text available
Large errors in peak discharge estimates at catchment scales can be ascribed to errors in the estimation of catchment response time. The time parameters most frequently used to express catchment response time are the time of concentration (TC), lag time (TL) and time to peak (TP). This paper presents a review of the time parameter estimation method...
Article
Full-text available
Biomass is a potential sustainable source of energy. Approximately one-third of the energy available from sugarcane is contained in the tops and leaves (trash), which are generally either burnt prior to harvesting or are not recovered from the field. Based on results reported in the literature and assuming a 50% trash recovery efficiency, it is est...
Article
Full-text available
The estimation of design floods is necessary for the design of hydraulic structures. Commonly used event-based approaches to design flood estimation have several limitations, which include the estimation of antecedent soil moisture conditions and the assumption that the exceedance probability of the design flood is the same as the exceedance probab...
Chapter
Sugarcane is a high biomass energy crop; the sugar stored in the stalk and the lignocellulosic residue remaining after sugar extraction called bagasse can both be used for the production of biofuel or other bioproducts. This chapter first talks about environmental requirements for sugarcane production, such as climate change and soil type. Next, it...
Article
There are limitations in conventional beef cattle management practices in South African feedlots. This is due to a lack of an adequate system for monitoring and controlling activities when handling cattle. In order to find a solution to these limitations, this document outlines a literature review to investigate an alternative automated system usin...
Article
Full-text available
The estimation of design floods is necessary for the design of hydraulic structures and to quantify the risk of failure of the structures. Most of the methods used for design flood estimation in South Africa were developed in the late 1960s and early 1970s and are in need of updating with more than 40 years of additional data currently available an...
Article
A continuous simulation modelling approach to design flood estimation has many advantages and overcomes many limitations of commonly used design event approaches. A major concern with continuous simulation using a hydrological model is the scale at which modelling should take place. According to researchers, the level of representation that will pr...
Article
Full-text available
In this study a daily to hourly rainfall disaggregation model developed in Australia has been modified and applied in South Africa. The structure of the model allows for the generation of 480 different temporal rainfall distributions varying from uniform to very peaked. The model was independently tested at 15 locations in differing climatic region...
Article
In South Africa, the demand for water exceeds available supplies in many catchments. In order to justify existing water requirements and to budget and plan in the context of growing uncertainty regarding water availability, a model to assist in the assessment and management of catchment water supply and demand interactions, and the associated impac...
Article
Full-text available
Long sequences of rainfall at fine spatial and temporal detail are increasingly required, not only for hydrological studies, but also to provide inputs for models of crop growth, landfills, tailings dams, liquid waste disposal on land and other environmentally sensitive projects. Rainfall information derived from rain gauges, radar or satellites ma...
Article
Full-text available
A Hydrological Decision Support Framework (HDSF) is being developed within a Water Research Commission (WRC) -funded project. The HDSF is intended as an integrated modelling tool for use by water resource managers and catchment management agencies (CMAs) in assessing and managing water resources. The HDSF will facilitate linking and running models...
Article
Full-text available
Labour for sugarcane cutting in South Africa is expected to become scarce as a result of growth in the manufacturing sector and the effect of HIV/AIDS on the available workforce. Manual harvesting is often favoured or unavoidable because of steep slopes and the high costs associated with mechanical harvesting. A brush-cutter with a redesigned blade...
Article
Long sequences of rainfall at fine spatial and temporal details are increasingly required, not only for hydrological studies, but also to provide inputs for models of crop growth, land fills, tailing dams, liquid waste disposal on land and other environmentally-sensitive projects. Rainfall information derived from raingauges, radar or satellites ma...
Article
Full-text available
River stage or flow rates are required for the design and evaluation of hydraulic structures. Most river reaches are ungauged and a methodology is needed to estimate the rates of flow, at specific locations in streams where no measurements are available. Flood-routing techniques are utilised to estimate the stages, or rates of flow, in order to pre...
Article
Full-text available
The objective of this paper is to illustrate the scope, uniqueness and opportunities for Agricultural Engineering and to present an overview of Agricultural Engineering education in South Africa. The need for engineers in South Africa is assessed, and the output from the schooling system in South Africa to meet this need is illustrated. Thereafter,...
Article
Several recent literature reviews highlight the need for improvements in procedures for design flood estimation [Cordery, I., Pilgrim, D.H., 2000. The state of the art of flood prediction. In: Parker, D.J. (Ed.), Floods. vol. II. Routledge, London, UK, pp. 185–197; Smithers, J.C., Schulze, R.E., 2001. Design runoff estimation: a review with referen...
Conference Paper
Full-text available
There is a sense of urgency to encourage students in the U.S. to embark on some form of study abroad experience. A whole semester or year abroad is a deterrent for many students because of the relatively large time commitment in an unknown environment and also because of concerns regarding completion of degree requirements. In this paper a short-te...
Article
Full-text available
In South Africa, the demand for water exceeds available supplies in many catchment areas. As a result, farmers face increasing pressure to use water more effectively, to justify existing water requirements and to budget and plan with growing uncertainty regarding water availability. Therefore, a tool to manage and assess catchment water supply and...
Article
Full-text available
Accurate estimates of design rainfall are essential inputs in water resource planning and engineering design. The duration of design rainfall which is required for design flood estimation may range from as short as 5 min for small urban catchments which have a rapid hydrological response, to a few days for large regional scale flood studies. In Sou...
Article
Full-text available
The exceptionally heavy rains which fell over the north-eastern parts of South Africa, Mozambique and Zimbabwe during February 2000 resulted in disastrous flooding, loss of hundreds of lives and severe damage to infrastructure. The objective of the study reported in this paper is to assess the severity, from a probabilistic perspective, and spatial...
Article
Full-text available
Copyright: 2003 Academy of Science of South Africa The principal activities of South African researchers in hydrology and water resources during the reporting period have been concerned with ground- and surface-water interactions, rainfall-runoff modelling, and the establishment of improved regional water resource databases, the management of trans...
Article
Full-text available
Relatively few recording raingauges with long, reliable records are available in South Africa for the estimation of short duration (≤24 h) design rainfalls. Hence, approaches to estimating short duration design rainfalls have been developed for South Africa which are based on daily rainfall data measured by standard, non-recording raingauges at fix...
Article
Full-text available
A regional frequency analysis of annual maximum series (AMS) of flood flows from relatively unregulated rivers in the KwaZulu-Natal province of South Africa has been conducted, including identification of homogeneous regions and suitable regional frequency distributions for the regions. The study area was divided into two homogeneous regions based...
Article
Full-text available
Accurate estimates of design rainfall are essential input in the design of hydraulic structures. Design rainfalls in South Africa for durations of 1 day and longer were last computed using a single station approach in the early 1980s. Currently longer periods of data are now available for analysis. Moreover, techniques for estimating design values...
Article
Full-text available
Use of the index-flood method at ungauged sites requires methods for estimation of the index-flood parameter at these sites. This study attempts to relate the mean annual flood to site characteristics of catchments in KwaZulu-Natal, South Africa. The ordinary, weighted and generalised least square methods for estimating model parameters are compare...
Article
The network of recording raingauges in South Africa with long records is relatively sparse and only 55 out of a total of 412 raingauges currently have record lengths longer than 30 years. In addition, much of the digitised rainfall data from numerous stations are viewed as being unreliable, with important events missing and errors in the digitised...
Article
Relatively few recording rainguages with long, reliable records are available in South Africa for the estimation of short duration (≤24 h) design rainfalls. Hence approaches to estimating short duration design rainfalls have been developed which are based on daily rainfall data measured by standard, non-recording raingauges at fixed 24 h periods en...
Article
Full-text available
The potential of using streamflow simulated by a continuous model to estimate design floods at ungauged sites in KwaZulu, South Africa is investi­ gated. The ACRU model was selected and simulated daily volume and peak dis­ charge was verified against observed data at two sites. Design floods computed from the simulated output compared well with tho...
Article
Short-duration design rainfall estimates are vital in the design of hydraulic structures and for environmental management. The use of a digitised rainfall database is expected to improve these estimates in Southern Africa. In order to estimate design rainfall intensities, an appropriate probability distribution has to be chosen, which adequately fi...
Article
Full-text available
The water budget of the Ntabamhlope wetland is investigated with particular emphasis on the estimation of the evaporation and ground­ water components of the wetland water budget. Evaporation is estimated using diurnal fluctuations of the water table in conjunction with the measured water retention characteristics of the soil. The estimation of gro...
Article
The ability to simulate, on a continuous basis, the peak flow rate, runoff volume and hydrograph from a catchment is important in planning, design and operation of hydraulic structures and the solution of a wide range of problems associated with water use. The ACRU modelling system, developed originally essentially as a small catchments daily time...
Article
Full-text available
Labour for sugarcane cutting in South Africa is expected to become scarce as a result of rising aspirations, growth in the manufacturing sector and the effect of HIV/AIDS on the available work force. Manual harvesting in the South African sugar industry is often favoured or unavoidable because of steep slopes and the high cost of mechanical harvest...
Article
Full-text available
Manual cattle handling systems are widely used in South Africa. A literature review and consultations were conducted to assess the advantages and disadvantages of various cattle handling systems with the objective of developing a more efficient system that incorporates automation, electronics and Radio Frequency Identification (RFID) technology. Th...

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Projects

Projects (3)
Project
The primary objective of this project is to develop a regionalised approach to estimate areal reduction factors and catchment response time parameters for improved design flood estimation at medium to large catchment scales in South Africa using the pilot scale studies of Pietersen (2016) and Gericke and Smithers (2016b; 2017) as guiding reference.
Project
The South African Water Research Commission has provided funding for the development of a probabilistic Rational Method in South Africa. The goals of the project include: 1. Collection, cleaning and flood frequency analysis of local flow measurements; 2. Identification of homogeneous flood producing regions utilising either clustering or region of influence regionalisation approaches; 3. Regional calibration of the rational method; 4. Development of regional regressions or geospatial mapping for estimation of the runoff coefficient; 5. Assessment of the model estimates against measured flows; and 6. Development of a utility for the application of the method.