Development of frequency models for predicting design storms in Lake Baringo drainage basin in Kenya

Abstract

Frequency models for estimating design storms for catchment management were developed in the present study using Extreme Value Type I (EVI) frequency distribution. The area chosen for the study was Lake Baringo drainage basin in Kenya. This basin is located in five different agro-climatic zones. Representative stations with at least 30 year data records were used in the study. Frequency models were developed for each station and design storms predicted for 2-year, 5-year, 10-year, 25-year, 50-year and 100-year return periods. The results revealed that semi-arid areas have higher design storms than humid areas although they receive less annual rainfall. A comparison was made between these design storms and those derived from Intensity-Duration-Frequency (IDF) curves. Discrepancies were observed between these two methods. This shows that although the use of IDF curves gave reasonable results, however better results can be achieved from models developed using historical data. Therefore, in areas where historical data are available, models should be preferred to IDF curves in estimating design storms.


Keywords: Frequency models, lake Baringo, Kenya, design storm


Botswana Journal of Technology Vol.13(1) 2004: 1-6