A decision support toolbox for automated channel sizing

Abstract

Flooding, a major natural hazard, results in significant economic losses and endangers human lives globally. In Uganda, manual channel sizing methods often lead to inaccuracies due to complex local hydrological processes, exacerbating flood risks and causing infrastructure damage. This research aims to develop an automated decision support toolbox to improve channel sizing accuracy, integrating advanced hydrological models tailored for Ugandan catchments. The primary objective is to create a toolbox that assists professionals in precise channel sizing, flood discharge determination, and flood extent prediction. The study focuses on the Sironko River basin, employing the TRRL East African Flood Model for rainfall-runoff analysis. This model, designed for East African catchments, addresses data scarcity and regional hydrological complexities. The methodology involves mixed research approaches, combining qualitative and quantitative data. Historical rainfall data, catchment characteristics, and channel geometry are analyzed using MATLAB. The TRRL model's iterative process refines rainfall-runoff estimations, ensuring accurate peak discharge predictions. Calibration and validation were performed using observed discharge data from 1990 to 2011 for calibration and 2012 to 2019 for validation. The model's initial peak discharge was adjusted from 216.16 m³/sec to 16.4990 m³/sec, achieving a 4.5% discrepancy. During validation, the simulated discharge was 21.53 m³/sec with a 4.56% difference from observed values, indicating robust model accuracy. With the obtained discharge value, flood extents or various flooding areas are sited out where 1D modelling of the flood was used in the MATLAB code using the Saint Venant Equations with segments also obtained along the river where the channel cross sections are to be obtained and saved in an excel document. The flood extents are plotted and visualized helping the user spot out the affected points of the natural channel.The obtained discharge and cross sections of affected points or areas along the river are to be fed into the channel sizing tool where hydraulic calculations based on open channel flow knowledge are carried out by the tool giving the most optimal channel cross section that may convey flow in it without flooding based on the design discharge given. The search for obtaining the most optimal channel cross section, channel dimensions or geometry are altered basing on either the slope or width or depth. The toolbox incorporates functionalities for watershed delineation, flood hazard mapping, and channel design, enhancing flood risk assessment capabilities. The findings demonstrate the TRRL model's effectiveness in providing accurate discharge estimates for Ugandan catchments. The developed toolbox offers a user-friendly interface for efficient channel design, contributing to improved flood mitigation strategies and infrastructure planning. The adoption of automated tools and advanced modeling techniques, as demonstrated in this research, is essential for enhancing the accuracy and reliability of channel design in Uganda.