摘要：The application of runoff models that rely on calibration
to future land use and climate conditions is
restricted to situations where the reaction of Hydrologic
Response Units to environmental change is
known. This limitation and the ensuing uncertainty
of model results can be avoided when a risk-based
approach to landscape and runoff analysis is taken.
GIS-based landscape analysis provides the possibility
of assessing the risks associated with non-linear
responses of Hydrologic Response Units to changing
rainfall and land use. In this paper, a runoff module
designed for IDRISI-Andes to calculate runoff
amount and routing for single or multiple rainfall
events on a hillslope at small catchment scale is presented.
The module is raster-based and uses layers
with topographic and hydrological parameters to calculate
a spatially distributed output layer of surface
runoff. Conceptually, the module extrapolates point
data of infiltration capacity onto a field or hillslope. A
spatially distributed runoff map is calculated based on
the addition of layers with rainfall data and the routing
of runoff through pathways connecting pixels in a digital
elevation model. Unlike outlet-based runoff modeling,
the need for parameterization of the catchment
is kept to a minimum. The application of the RUNOFF
module in a test area in the Eifel region of Germany
indicated that runoff from grassland is sensitive to
small increases in rainfall intensity and soil compaction.
The spatial patterns of infiltration capacity also
contribute significantly to the non-linearity of the test
area reaction to changing rainfall and soil hydrologic
properties.
