Comparison of SCS and Green-Ampt Distributed Models for Flood Modelling in a Small Cultivated Catchment in Senegal

Abstract

The vulnerability to floods in Africa has increased over the last decades, together with a modification of land cover as urbanized areas are increasing, agricultural practices are changing, and deforestation is increasing. Rainfall-runoff models that properly represent land use change and hydrologic response should be useful for the development of water management and mitigation plans. Although some studies have applied rainfall-runoff models in West Africa for flood modelling, there is still a need to develop such models, while many data are available and have not still been used for modelling improvement. The Ndiba catchment (16.2 km 2 ), which is located in an agricultural area in south Senegal, is such catchment, where a lot of hydro-climatic data has been collected between 1983 and 1992. Twenty-eight flood events have been extracted and modelled by two event-based rainfall-runoff models that are based on the Soil Conservation Service (SCS) or the Green-Ampt (GA) models for runoff, both coupled with the distributed Lag and Route (LR) for routing. Both models were able to reproduce the flood events after calibration, but they had to account for that the infiltration processes are highly dependent on the tillage of the soils and the growing of the crops during the rainy season, which made the initialization of the event-based models difficult. The most influent parameters for both models (the maximal water storage capacity for SCS, the hydraulic conductivity at saturation for Green-Ampt) were mostly related to the development stage of the vegetation, described by a Normalized Difference Vegetation Index (NDVI) anomaly. The SCS model performed finally better than the Green-Ampt model, because Green-Ampt was very sensitive to the variability of the hydraulic conductivity at saturation. The variability of the parameters of the models highlights the complexity of this kind of cultivated catchment, with highly non stationary conditions. The models could be improved by a better knowledge of the tillage practices, and a better integration of these practices in the parameters predictors. The small agricultural area Thysse Kaymor is one of these catchments that have not been the object of modelling studies at the catchment scale, despite that many hydro-climatic data have been collected. Five nested catchments have been monitored during the period 1982-1992, including rainfall, runoff, and water content and hydrodynamic properties of the soils. The role of the agriculture on the runoff was clearly shown by [11], who claimed that the runoff conditions are first high before the tillage, and then reduce along the rainy season due to the growth of the crops. They also found that the Normalized Difference Vegetation Index (NDVI) could be a good predictor of the runoff conditions. However, modelling was only performed at the plot scale [12], and not at the catchment scale.The aim of this study is to assess the skill of two well-known event-based models-the Soil Conservation Service (SCS) model and the Green-Ampt (GA) model in...

A Simple GIS-Based Model for Urban Rainstorm Inundation Simulation

“…The rainfall-runoff was calculated with the SCS model. The SCS model has been widely used to estimate runoff for small catchments [40][41][42]. It was developed based on a water balance relationship, Equation 1, and two basic hypothesizes, i.e., (1) the proportional equalization or linear hypothesis of Equation 2, and (2) the hypothesized relationship between the initial loss and potential maximum retention of Equation 3.…”

Hydrological Hazard: Analysis and Prevention

“…Among the 13 articles published in the Special Issue, 1 is a Technical Note (Terranova et al [4]), 11 are Research Articles [5][6][7][8][9][10][11][12][13][14][15], and one is a Case Report (Schmid-Breton et al [16]). Figure 1 compares the geographic distribution of the authors and research teams publishing in the Special Issue (Figure 1a), as well as of the case studies and demonstration sites ( Figure 1b).…”

“…Bouvier et al [8] analyzed the skill of two well-known event-based models, the Soil Conservation Service model and the Green-Ampt model, in reproducing the flood processes in a semi-arid agricultural catchment of Senegal (Ndiba). In particular, twenty-eight flood events have been extracted and modelled.…”

“…Word cloud of the keywords published in the papers[4][5][6][7][8][9][10][11][12][13][14] of this Special Issue.…”

Feasibility Investigation of Improving the Modified Green–Ampt Model for Treatment of Horizontal Infiltration in Soil

“…With the advantages of having a reasonable physical mechanism and easy-to-solve quantitative expressions, the GA model has been widely used in water infiltration calculations for a number of hydrologic scenarios, including homogeneous soil [10], inhomogeneous soil [11][12][13][14][15], ponding sites [16], non-ponding sites [17][18][19][20], steady rainfall, and unsteady rainfall [21,22]. In addition, several methods have been proposed for determining key parameters of the GA model [23][24][25][26].…”