Simulating the effects of forest roads on watershed hydrology
The Distributed Hydrology-Soil-Vegetation Model (DHSVM) was enhanced to represent the interception and redirection of surface and subsurface flow by road cuts and stream channels. Two channel networks are imposed in vector form on the DHSVM grid: one representing roads, the other representing streams. Impacts of the road network on channel flows are modeled explicitly; road location and geometry, along with soil moisture, determine the timing and volume of intercepted water, while road drainage characteristics and culvert placement determine the flow path and travel time to the channel system. The active road drainage/channel network may expand and contract as grid cell water tables rise and fall below their channel beds. The model was applied to a 10-km2 experimental watershed to study the influence of road network design on streamflow characteristics. It was demonstrated that even where the road network produces minor changes in streamflow at the basin outlet, subsurface flow interception by roads could alter significantly streamflow in tributary channels. The impact of the road network on channel flows was shown to vary during a storm based on the road design, storm characteristics, topography, local geology, and soil moisture conditions. The impact occurs earlier in a storm when the road network diverts flow into the drainage rather than out of it. When flows are redirected into a channel, the road contributing area quickly increases the current total contributing area for the channel, causing a proportional increase in discharge. If the road design allows some water to pass under the road, there may be only minor impacts early in the storm with increasing impact as watertables rise and subsurface flow begins to be intercepted. When flows are redirected out of the natural drainage the impact is not felt until the channel contributing area extends upslope to the road system.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 886725
- Report Number(s):
- PNNL-SA-43007; TRN: US200616%%1128
- Resource Relation:
- Related Information: Land Use and Watersheds: Human Influence on Hydrology and Geomorphology in Urban and Forest Areas, Water Science and Applications Series, 2(127-143
- Country of Publication:
- United States
- Language:
- English
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