Geomorphic controls on the physical and hydrologic properties of soils in a valley floor

The distribution of soil hydraulic and physical properties strongly influen ces runoff processes in landscapes. Although much work has been done to qua ntify and predict the properties of hillslope soils, far less is known abou t the distribution of soil properties in valley floors. A technique that li nks the estimation and distribution of soil hydraulic properties in valleys , with easily identified geomorphic features, was developed along a 2 km le ngth of a valley at Brooks Creek in New South Wales, Australia. Soil physic al and hydraulic property data were collected across a set of floodplain an d fan features within the valley and analysed statistically to determine if soil properties varied significantly between geomorphic features and strat igraphic layers. The results show that the depth-averaged saturated hydraulic conductivity, K-s, of the soil varies significantly with landform: fan units have K-g val ues that are twice that of floodplains and colluvial toeslope deposits have K-s values four times higher than floodplains. Given the notorious variabi lity of K-s values in space, the strong statistical separation of soil prop erties by landform, backed up by strong separation of soil particle size by landform, suggests a way forward in understanding the distribution of soil properties in valleys and their influence on catchment hydrology. Copyrigh t (C) 2000 John Wiley & Sons, Ltd.