Location: Northwest Watershed Management Research
Title: Characteristics of concentrated flow hydraulics for rangeland ecosystems: implications for hydrologic modeling Authors
|Al-Hamdan, Osama -|
|Kormos, Patrick -|
|Boll, Jan -|
Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2011
Publication Date: February 3, 2012
Citation: Al-Hamdan, O.Z., Pierson Jr, F.B., Nearing, M.A., Stone, J.J., Williams, C.J., Moffet, C.A., Kormos, P.R., Boll, J., Weltz, M.A. 2012. Characteristics of concentrated flow hydraulics for rangeland ecosystems: Implications for hydrologic modeling. Earth Surface Processes and Landforms. 37(2):157-168. Interpretive Summary: Historical rangeland model parameterization of concentrated flow processes has relied on the extensive studies conducted to describe rill or concentrated flow hydraulics on croplands. This leads to less accurate predictions as rangelands and croplands have different soil and vegetation cover characteristics. We examined the hydraulics of concentrated flow using field experimental data over diverse rangeland landscapes, and developed new empirical prediction models of different rangeland concentrated flow hydraulic parameters. The main variables that are required to apply these equations are readily available from ecological sites, soils, and vegetation characteristics. Such data is routinely collected by range managers and scientists. Thus, these predictive equations can be robustly applied for estimating concentrated flow hydraulic parameters as inputs for hydrology and erosion models of diverse rangeland ecosystems.
Technical Abstract: Concentrated flow is often the dominant source of water erosion following disturbance on rangeland. Because of the lack of studies that explain the hydraulics of concentrated flow on rangelands, cropland-based equations have typically been used for rangeland hydrology and erosion modeling, leading to less accurate predictions due to different soil and vegetation cover characteristics. This study investigates the hydraulics of concentrated flow using unconfined field experimental data over diverse rangeland landscapes within the Great Basin Region, United States. The results imply that the overall hydraulics of concentrated flow on rangelands differ significantly from those of cropland rills. Concentrated flow hydraulics on rangelands are largely controlled by the amount of cover or bare ground and hillslope angle. New predictive equations for concentrated flow velocity (R2=0.51), hydraulic friction (R2=0.56), and width (R2=0.4) representing a diverse set of rangeland environments were developed. The resulting equations are applicable across a wide span of ecological sites, soils, slopes, and vegetation and ground cover conditions and can be used by physically-based rangeland hydrology and erosion models to estimate rangeland concentrated flow hydraulic parameters.