Effects of underlay on hill-slope surface runoff process under different
rainfall intensities
Abstract
Clarifying the impact of underlay (i.e., the combination of understory
vegetation and surface micro-topography) on the surface runoff process
under different rainfall intensities would provide a significant
theoretical basis for controlling soil and water loss on steep slopes in
mountainous areas of southwestern China. In the current study, the
runoff process under different rainfall intensities was observed based
on 10 natural runoff plots, and the correlation between the spatial
pattern of cypress (Cupressus funebris), micro-topography and runoff
characteristic parameters was tested using the Pearson correlation
coefficient method. The effects of the spatial pattern of cypress and
micro-topography on surface runoff also were analyzed using the Response
Surface Method (RSM). The results indicated that the blocking effects of
different underlay conditions on surface runoff decreased with the
increase of rainfall intensity. The impact of the spatial pattern of
cypress and micro-topography on the runoff process was mainly reflected
in the impact on peak flow. Under the condition of moderate rainfall
(30-50 mm/24 h) or rainstorm (50-70 mm/24 h), topographic relief,
surface roughness, runoff path density, contagion index of cypress, and
stand density of cypress were the key factors that affected the peak
flow, whereas under the condition of severe rainstorms (>
70 mm/24 h) none of the foregoing factors had a significant correlation
with peak flow. Under the conditions of moderate rainfall or rainstorm,
when the composite indexes of the spatial pattern of cypress and
micro-topography were small, the peak flow would not be significantly
affected. When the micro-topography reached the conditions required to
significantly increase the peak flow, increasing the composite index of
the spatial pattern of cypress within a certain range promotes the peak
flow, and when the composite index of the spatial pattern of cypress
exceeded a certain value, as the composite index of micro-topography
increased, the dominant factor affecting the peak flow gradually changed
from the spatial pattern of cypress to that of micro-topography.