The effects of riparian protection on channel form and stability of 6 grazed streams, Southland, New Zealand / by R. Bruce Williamson, R. Keith Smith and John M. Quinn.

"September 1990."

Includes 38 bibliographical references (p. 36-39) ; 16 figs; 4 tables; 1 appendix.

The effects of grazing animals on stream margins and the benefits of riparian retirement to streambank erosion and aquatic habitat were assessed through the survey of 6 streams and rivers in Southland, New Zealand. Effects and benefits were assessed by comparing morphological and vegetation data between grazed and retired reaches, and making inferences about channel erosion processes and the effect on those characteristics that benefit aquatic habitat. Grazing was found to have relatively little effect on channel morphology and bank stability of most streams. Only in the most damaged situation had significant channel widening occurred. We attributed the relatively low degree of grazing damage in most streams compared with that observed overseas to the relatively dry stream-side soils, moist temperate climate, high inaccessible banks and possibly better stock management. The lack of recolonisation by native species,particularly larger shrubs or trees that might stabilise banks and enhance instream habitat, leads us to suggest that greater benefits would accrue if the retired zones were planted in appropriate species. This would seem to be a particularly attractive option in larger streams where an improvement in trout fisheries and a reduction in erosion is required. (auth)