The flood hazard in the lower reaches of the Sondu/Miriu river

Abstract

This dissertation is on the flood hazard on the River Sondu floodplain which is structurally continuous with the Kano Plains in Kisumu District. The incidence of floods has become greater in the recent past. First, the study attempts to establish whether the greater incidence of flooding can be attributed to changes in river flow characteristics and predict floods of various discharges. Second an attempt to establish the reasons that keep people living on the floodplain inspite of the eminent danger involved and to examine the factor! that determine flood damage control measures known to and adopted by individuals is made. Hydrological data was obtained from three gauging stations on the river whilst the socio-economic data came from interviews with people living on the floodplain. The hydrological data is used to produce hydrographs, rating curves and flood-frequency curves. One-way analysis of variance is used to test changes overtime. The socio-economic data is used:to establish relationships between the nature and number of adjustments to the hazard adopted by individuals on the one hand and their levels of income and education, sources of income and frequency of exposure to flooding on the other It was found that whereas the discharge from the river has not changed significantly,. lower discharges (than before) cause flooding. This suggests that the channel capacity in the lower course of the river has been reduced. It was also found that continued occupance of the floodplain is related to fishing and activities dependent on it. Analysis of the data showed that the less educated and the poor are more reluctant to leave the floodplain and that those people who live in the greater risk zones know and practice more flood damage control measures. In view of these findings it is recommended that floodplain, managers emphasize 'within channel' and bank protection' methods of flood control and that enviromental conservation measures be enhanced within the floodplain and in the rest of the Sondu river catchment particularly in the highland source regions. Finally the victims need to be involved in the fl60d control activities to give them that sense of participation in the determination of their own destiny and the priority in the Sondu-river floodplain should be flood-damage control rather than flood control.