FLOOD DAMAGE REDUCTION ANALYSIS: (CASE STUDY ON RIBB CATCHMENT, FOGERA FLOOD PLAIN)

Abstract

Fogera flood plain, located at the foot of Ribb catchment, has been repeatedly devastated by powerful flash floods. As the flood pass through center of the flood plain, it causes tremendous losses in terms of life and property. Even though various mitigation measures were undertaken so far, they are not adequate to withstand the flood threats. Hence, this study carried out flood damage reduction analysis in order to evaluate and identify the competent flood mitigation plans. The required components for this analysis, flow frequency functions for each alternative flood control plans were generated by modifying watershed characteristics and geometry using HEC-HMS model. The output from HMS was then used to run the HEC-RAS model and generate water surface elevations. These functions were then used with HEC-FDA to compute expected annual damage and evaluate performance of the alternative flood damage reduction plans. Based on the result of flow-frequency analysis, implementations of detention pond and diversion control create significant impact on probability-discharge functions for the study area. The potential vulnerable areas for the 100 year return period flood event are Ambua Kokit kebele. Under the stated assumptions, the project that is most desirable from an economic viewpoint is diversion control flowed by detention pond. However, before making a final decision the social and political aspects also should be considered.