Investigation of Flood Hazards and Mitigation Measures in Lante Area of Gamo-Gofa Zone

Abstract

The perennial river "Basso", often experience flooding to inundate Lante and Omo­ Lante Kebele Peasant Associations (KPA) . Approximately 6 km reach of the Basso river , downstream of upper Basso and Dea confluence point , was studied to determine flood extents for probabilities 1 in 2, 5 , 10 , 15 , 25 , 50 and 100 years . After peak flood discharge estimation through Rational Method, flood boundary maps are simulated using Hydraulic Engineering Center River Analysis System (HEC RAS) model . In addition , significant causes of flooding such as heavy rains at upper escarpments ; decrease of channel conveyance efficiency ( by debris flow and land slides) ; over grazing in the hilly catchment ; deforestation and bank line cultivation are enumerated from analysis result of this paper .To set aside some additional nutrient enriched plot of land, dike construction with 50 m offset alignment from both bank lines is proposed as an alternative design option . Through this option, controlled inundation is attained .Besides the above structural stream regulation measure, canalization is the other measure ascertained to attain safe flow confinement within the natural stream Basso. The expected risk due to dike over flunking is considerably reduced by this canalization activity. With the aid of machine excavators dredging of debris and the silt accumulation is frequently taking place along Basso stream .To effect optimal flood plain development; non structural measures are also included to the extent of affordability. Afforestation program; educating the farmer about contour cultivation ; human activity regulation (i.e. punishment strategy for illegal bank line cultivation) and community awareness creation ( by establishing comprehensive public educational information programs are some of the measures to be integrated with aforementioned structural measures . This paper also proposes an integrated river basin development approach as the second phase of implementation following