The hydrological effects of fire in South African mountain catchments

Streamflow and its storm-flow elements in four catchments were analyzed by the paired catchment method for a response to fire. Prior to burning two of the catchments were vegetated with over-mature fynbos (the indigenous scrub vegetation of the southwestern Cape, South Africa), one was afforested with Pinus radiata and the fourth with 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-flow. Annual total flow increases of around 16% were in agreement with model predictions, being related to the reductions in transpiration and interception. The manner of streamflow generation appeared to have remained unaltered despite the presence of some water repellency in the soils and consequent overland flow on some steep midslope sites. The two timber plantation catchments experienced large and significant increases in storm-flows and soil losses, while total flow increased by 12% in the pine catchment and decreased marginally in the eucalypt catchment. The pattern of the storm-flow increases was similar in both cases. After fire, storm hydrographs were higher and steeper though their duration was little changed. The respective first year increases in the pine and eucalypt catchments were 290% and 1110% for peak discharge, 201% and 92% for quick-flow volume, and 242% and 319% for storm response ratio. These fire effects are considered to be due to changes in storm-flow generation consistent with an increased delivery of overland flow (surface runoff) to the stream channel. This was caused, in part, by reduced infiltration resulting from water repellency in the soils of the burned catchments. Overall the hydrological effects of fire are related to numerous interactive factors, including the degree of soil heating, the vegetation type and soil properties.

[1]  L. Debano.  Water repellent soils: a state-of-the-art , 1981 .

[2]  J. Hewlett,et al.  A REVIEW OF CATCHMENT EXPERIMENTS TO DETERMINE THE EFFECT OF VEGETATION CHANGES ON WATER YIELD AND EVAPOTRANSPIRATION , 1982 .

[3]  D. Versfeld.  Overland Flow on Small Plots at the Jonkershoek Forestry Research Station , 1981 .

[4]  J. Hewlett.  Rainfall at the Jonkershoek Forest hydrological research station , 1971 .

[5]  D. Scott,et al.  The Effects of Fire on Soil Water Repellency, Catchment Sediment Yields and Streamflow , 1992 .

[6]  B. V. Wilgen,et al.  A model for comparing water yield from fynbos catchments burnt at different intervals , 1986 .

[7]  D. V. Wyk.  Some effects of afforestation on streamflow in the Western Cape Province, South Africa , 1987 .

[8]  H. Rycroft.  A NOTE ON THE IMMEDIATE EFFECTS OF VELDBURNING ON STORMFLOW IN A JONKERSHOEK STREAM CATCHMENT , 1947 .

[9]  D. Richardson,et al.  Fire in South African Mountain Fynbos: Ecosystem, Community and Species Response at Swartboskloof , 1992 .

[10]  C. J. Leitch,et al.  Erosion and nutrient loss resulting from Ash Wednesday (February 1983) wildfires a case study , 1983 .

[11]  I. Moore,et al.  Soil hydrophobic effects on infiltration and catchment runoff , 1989 .

[12]  Jan M. H. Hendrickx,et al.  Water and solute movement in a coarse-textured water-repellent field soil , 1990 .

[13]  R. Schulze,et al.  The Hydrological Effects of a Wildfire in a Eucalypt Afforested Catchment , 1992 .

[14]  Leonard F. DeBano,et al.  WATER REPELLENT SOILS AND THEIR RELATION TO WILDFIRE TEMPERATURES , 1966 .

[15]  David F. Scott,et al.  The effects of wildfire on soil wettability and hydrological behaviour of an afforested catchment , 1990 .

[16]  D. Kleinbaum,et al.  Applied Regression Analysis and Other Multivariate Methods , 1978 .

[17]  H. W. Anderson,et al.  FORESTS AND WATER. effects of forest management on floods, sedimentation, and water supply , 1976 .

[18]  G. Giovannini,et al.  EFFECT OF FIRE ON HYDROPHOBIC AND CEMENTING SUBSTANCES OF SOIL AGGREGATES1 , 1983 .

[19]  J. Brown,et al.  Hydrologic effects of a bushfire in a catchment in south-eastern New South Wales , 1972 .

[20]  L. Debano.  The Effect of Hydrophobic Substances on Water Movement in Soil during Infiltration 1 , 1971 .

[21]  P. Cheney,et al.  Fire in forestry. Volume 1. Forest fire behavior and effects. Volume 2. Forest fire management and organization. , 1983 .