The Origin of overland flow in Otutaru Catchment

Abstract

Data collected from 14 runoff plots and Otutaru catchment indicate that there is a very close relationship between runoff measured at the plots, and rates and volumes recorded at the outlet from Otutaru catchment. This ' relationship is dependent principally on rainfall intensity and is influenced by soil moisture conditions before and during a storm. The influence of aspect, storm direction and wind speed are analysed and it is deduced that they are minor influences on runoff. It is concluded that overland flow is generated throughout Otutaru catchment when rain of sufficient intensity occurs. Initially the bulk of this flow is lost by infiltration in the valley bottom but after rain of a certain volume or sufficient intensity has fallen the whole catchment appears to contribute to Otutaru runoff. The slopes produce relatively greater flow, but all areas contribute significantly to catchment runoff.