Suitability of Flood Hazard Assessment Methods for Tanzania: A Case of Little Ruaha and Upper Ngerengere Catchment

Abstract

Understanding the applicability of flood quantile estimation methods in flood hazard assessment is fundamental for planning, prevention, and management of flood risks. Therefore, this study evaluates and compares three hydrological methods, namely Hydrologiska Byråns Vattenbalansavdelning (HBV), Soil Conservation Service-Curve Number (SCS-CN), and regional regression equation (RRE), to estimate flood quantiles embedded in the existing flood damage assessment framework by applying them to two different river catchments, Little Ruaha (LR) and Upper Ngerengere (UN), Tanzania. The evaluation of method performance was carried out using three standard statistical measures for data from 1954 to 2010 and the 1971–1988 period in LR and UN catchments (LRC and UNC). The findings indicated that no single approach could fit all catchments and return periods for these case studies. Overall performance indicated that the RRE method provides more accurate and consistent quantile estimates than other approaches. These findings indicate that spatial scale, model structure, parameters, and hydro-climatic data condition are the most important elements influencing the suitability of the supplied methods for flood risk assessments, which serve as the foundation for developing an improved flood damage assessment framework.

Keywords: Flood Quantiles; Estimate Methods; Flood Risk Management; Little Ruaha; Ngerengere