A description, quantification and characterization of hillslope hydrological processes in the Weatherley catchment, Eastern Cape Province, South Africa.
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Date
2013
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Abstract
Advances in hillslope hydrology have been numerous in the past two decades. However many of these
advances have been highly site specific in nature, without identifying any means of linking processes
across different spatial scales. Meaningful Prediction in Ungauged Basins (PUB) requires the
understanding and observation of processes across a range of scales in order to draw out typical
hydrological controls. Contempory tracer based methods of quantifying a combination of hillslope
processes have identified hillslope geology as the main determinant in different catchment response types.
A range of hillslope scale models have been developed in the last 20 years, using different levels of detail
to simulate hillslope hydrological responses. Often the data heavy requirements of hillslope scale models
make them impractical to apply at larger scales. While catchment scale models lack the ability to represent
hillslope scale processes. In order to overcome this, a scale applicable model with the ability to represent
hillslope and catchment dynamics is required to accurately quantify hillslope and catchment hydrological
processes. This study aims to characterize typical hillslope soil type responses through inferring qualitative
hillslope descriptions into a numerical catchment scale model allowing for lateral subsurface routing
between adjacent soil horizons. Hydrometric and tracer observation are used to describe and quantify
dominant hillslope hydrological processes. Simplifications of hillslope process descriptions are used to
calibrate the model to represent the subsurface hillslope connectivity. Results show that hillslope scale
hydrological process characteristics can be faithfully simulated with quaternary scale climate, land use and
soils data, discriminating only between different hillslope soil types. The simplification of hillslope soils
into three distinct groups allows for the further derivation of dimensionless descriptors of hillslope
hydrological response using the Advection Dispersion Function. Slopes with shallower stratified soils
showed rapid responses to rainfall in the soil water, while those with deeper soils and less horizontal
stratification showed appreciably slower responses to rainfall, with older hillslope water dominating soil
water for longer periods. This identifies soils as a dominant determinant in hillslope runoff characteristics.
This allows for the characterization and ultimately a simplified classification of different hillslope soils and
their response types, which is applicable at a range of scales.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
Keywords
Slopes (Physical geography), Hydrology--Eastern Cape--Weatherley Watershed., Slopes (Soil mechanics), Hydrologic models., Theses--Hydrology.