Hydrological effects of clearing native forest in North-east Victoria: the first three years.  C. J. Leitch and D. W. Flinn.  December 1985.  21 pp. (unpubl.)

SUMMARY

A small steeply sloping, forested catchment (46.4 ha) in north-east Victoria was cleared of its native vegetation (except for a 30 m strip either side of the perennial stream) and the debris broadcast burnt before the catchment was planted with radiata pine (Pinus radiata D. Don).

Clearing caused variable increases in annual runoff in the first three years after treatment, with the magnitude of the increase depending on the amount and distribution of the rainfall received. Annual runoff was 365 mm or 85% higher than expected in the first year after clearing and 210 mm (19%) and 33 mm (73%) higher in the second and third years, respectively. In this locality, therefore, initially increases in annual runoff of between 30 mm and 400 mm can be expected, with increases of around 250 mm being most likely in years of average rainfall (approx. 1400 mm).

Analysis of pre- and post-treatment storm hydrograph data showed that clearing caused a significant overall increase in peak flows, with the size of the increases depending on the moisture status of the catchment soils. Substantial increases (two-fold) in peak flows were measured during the post-summer recharge phase. However, when catchment soils were moist in winter-spring, the period when most flooding occurs, peak flows of cleared catchments were not substantially different (+ 30%) from undisturbed catchments.

The results obtained indicate that overland flow had little influence on the storm hydrographs of these steeply sloping catchments either before or after clearing. The results are specific to sites with similar characteristics to those of the study area.

Also published:

Leitch, C.J. and Flinn, D.W. (1985)  Hydrological effects of clearing native forest in North-east Victoria: the first three years.  Aust. For. Res. 16(2): 103-116.