Identifying a common distribution for flood estimation in ungauged catchments in Botswana

Abstract

This paper attempts to identify a possible common statistical distribution, to model the annual maximum floods observed at various rivers and streams of Botswana using goodness of fit indices based on K-S Statistics and L-Moment Ratios. Results from the two approaches, suggest that Log-Normal distribution adequately describes the annual maximum flood series obtained from various gauged sites across the country and can possibly be used as a common distribution for estimation of flood quantiles at specified risks which can be used in design of various water resourcesand hydraulic structures across streams and rivers of Botswana. Based on the homogeneity criteria, two standardised curves have been developed for two catchment systems which can be used for the above purpose while dealing with ungauged basins in these systems.

Keywords: flood estimation, K-S Statistics, L-Moment Ratios, hydraulic structures, ungauged basins

Botswana Journal of Technology Vol. 14(2) 2005: 1-8