Do vegetation and soil buffer the effects of orographic precipitation on runoff and fluvial erosion?
Abstract
We explore the effects of orographic precipitation on runoff and fluvial channel evolution in Kohala, HI. Strong orographic precipitation should affect river discharge, erosion patterns and channel profile form. Furthemore, vegetation and soil influence the effective precipitation (Pe), or the amount of precipitation (P) contributing to runoff, mainly through infiltration and evapotranspiration. In Kohala we observe that a gradient in vegetation and soil type follows the precipitation gradient. High precipitation at the highest elevations produces a more robust vegetation cover such as evergreen forest, which could produce higher infiltration and evapotranspiration rates. Thus, we propose that in some regions, vegetation and soil might be a buffer which dampens the effects of orographic precipitation on runoff production patterns. In order to quantify the effects of vegetation and soil, we use a simple parameter, the runoff coefficent (Pe/P), to calculate effective precipitation. We use remote sensing data to make the land use and land cover classification (LULC) in Kohala. The LULC results are coupled with topography data, precipitation data (from PRISM) and soil texture data to estimate the runoff in Kohala, using a soil-vegetation-atmosphere transfer (SVAT) model coupled with a runoff model. Finally, we use the runoff as the input to a landscape evolution model to explore the sensitivity of channel form to variation in vegetation and soil patterns. We find that vegetation and soil patterns can influence the effects of orographic precipitation on river discharge, erosion, and profile patterns. Because the runoff coefficient varies with soil and vegetation, the elevation with the highest effective precipitation can occur in the upper, middle or downstream parts of the channel, even though the largest precipitation rate is always at the highest elevations. The highest concavity index is always where the effective precipitation is the highest. Our findings suggest that vegetation and soil gradients may follow precipitation gradients and buffer the effects of orographic precipitation on runoff and erosion patterns.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMEP53B0624H
- Keywords:
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- 1813 HYDROLOGY / Eco-hydrology;
- 1825 HYDROLOGY / Geomorphology: fluvial;
- 1847 HYDROLOGY / Modeling;
- 1860 HYDROLOGY / Streamflow