The hydrological effects of fire in South African catchments.
Loading...
Date
1994
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Stream-flow and storm-flow in four small catchments were analysed by the paired
catchment method for a response to fire. Two of the catchments were vegetated with
over-mature fynbos (the indigenous scrub vegetation of the south-western Cape Province,
South Africa), one was afforested to Pinus radiata and the fourth to Eucalyptus fastigata.
One of the fynbos catchments was burned in a prescribed fire in the late dry season. The
other catchments burned in wildfires.
Neither of the fynbos catchments showed a change in storm-flows. Annual total flow
increases of around 16% were in line with predictions, being related to the reductions in
transpiration and interception. The manner of stream-flow and storm-flow generation
appeared to have remained unaltered despite the fire.
The two timber plantation catchments experienced large and significant increases in stormflow
and sediment yields, while total flow increased by 12% in the pine catchment and
decreased marginally in the eucalypt catchment. After fire, storm hydrographs were higher
and steeper though their duration was little changed. These fire effects are considered to
be due to changes in storm-flow generation consistent with an increased delivery of
overland flow to the stream channel. This was caused, in part, by reduced infiltration
resulting from water repellency in the soils of the burned catchments.
The inherent wettability of a wide range of soil types and textures from beneath timber
plantations and other vegetation types over a broad geographic distribution in South Africa
was measured by four methods. Soils with high repellency ratings, unrelated to fire, are
common and are most likely to occur beneath plantations of Eucalyptus and Acacia spp.
and indigenous forest.
Water repellent soils played a role, at two of the three locations, in the generation of
overland flow from small plots exposed to simulated rainfall. However, the inherent
repellency of the dry soils was extreme, such that fire-induced water repellency was not
a factor in the response of the plots. The important role of fire in this experiment was in
burning-off of repellency in the surface layer of the soil and in removing ground cover.
Description
Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.
Keywords
Hydrology--South Africa., Hydrology--Computer programs., Fire ecology., Runoff--South Africa., Theses--Agricultural engineering.