<abstract xmlns="http://www.w3.org/1999/xhtml"><p> Drainage of paved and unpaved roads has been implicated as a major contributor of overland flow and erosion in mountainous landscapes. Despite this, few watershed models include or have tested for the effect roads have on discharge and sediment loads. Though having a model is an important step, its proper application and attention to distinct landscape features is even more important. This study focuses on developing a module for drainage from a road and tests it on a nested watershed (Shanko Bahir) within a larger previously studied site (Debre Mawi) that receives overland flow contributions from a highly compacted layer of soil on an unpaved road surface. Shanko Bahir experiences a sub-humid monsoonal climate and was assessed for the rainy seasons of 2010, 2011, and 2012. The model chosen is the Parameter Efficient Distributed (PED) model, previously used where saturation-excess overland flow heavily influences discharge and sediment concentration variation, though infiltration-excess occasionally occurs. Since overland flow on unpaved surfaces emulates Hortonian flow, an adjustment to the PED model (the developed module) advances possible incorporation of both flow regimes. The modification resulted in similar modeling performance as previous studies in the Blue Nile Basin on a daily basis (NSE = 0.67 for discharge and 0.71 for sediment concentrations). Furthermore, the road while occupying a small proportion of the sub-watershed (11%) contributed importantly to the early discharge and sediment transport events demonstrating the effect of roads especially on sediment concentrations. Considerations for the dynamic erodibility of the road improved sediment concentration simulation further (NSE = 0.75). The results show that this PED modeling framework can be adjusted to include unpaved compacted surfaces to give reasonable results, but more work is needed to account for contributions from gullies, which can cause high influxes of sediment.</p></abstract>

Drainage of paved and unpaved roads has been implicated as a major contributor of overland flow and erosion in mountainous landscapes. Despite this, few watershed models include or have tested for the effect roads have on discharge and sediment loads. Though having a model is an important step, its proper application and attention to distinct landscape features is even more important. This study focuses on developing a module for drainage from a road and tests it on a nested watershed (Shanko Bahir) within a larger previously studied site (Debre Mawi) that receives overland flow contributions from a highly compacted layer of soil on an unpaved road surface. Shanko Bahir experiences a sub-humid monsoonal climate and was assessed for the rainy seasons of 2010, 2011, and 2012. The model chosen is the Parameter Efficient Distributed (PED) model, previously used where saturation-excess overland flow heavily influences discharge and sediment concentration variation, though infiltration-excess occasionally occurs. Since overland flow on unpaved surfaces emulates Hortonian flow, an adjustment to the PED model (the developed module) advances possible incorporation of both flow regimes. The modification resulted in similar modeling performance as previous studies in the Blue Nile Basin on a daily basis (NSE = 0.67 for discharge and 0.71 for sediment concentrations). Furthermore, the road while occupying a small proportion of the sub-watershed (11%) contributed importantly to the early discharge and sediment transport events demonstrating the effect of roads especially on sediment concentrations. Considerations for the dynamic erodibility of the road improved sediment concentration simulation further (NSE = 0.75). The results show that this PED modeling framework can be adjusted to include unpaved compacted surfaces to give reasonable results, but more work is needed to account for contributions from gullies, which can cause high influxes of sediment.

Modeling sediment concentration and discharge variations in a small Ethiopian watershed with contributions from an unpaved road

Department of Biological and Environmental Engineering, Cornell University, Ithaca, 206 Riley Robb Hall, NY 14853-5701,

Faculty of Civil and Water Resources Engineering, Institute of Technology, Bahir Dar University, Bahir Dar,

Amhara Regional Agriculture Research Institute, Bahir Dar,

Department of Biological and Environmental Engineering, Cornell University, Ithaca, 206 Riley Robb Hall, NY 14853-5701, USA

Journal of Hydrology and Hydromechanics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Drainage of paved and unpaved roads has been implicated as a major contributor of overland flow and erosion in mountainous landscapes. Despite this, few...

Modeling sediment concentration and discharge variations in a small Ethiopian watershed with contributions from an unpaved road

Publié en ligne: 08 déc. 2016

Pages: 1 - 17

Reçu: 16 mai 2016

Accepté: 12 juil. 2016

DOI: https://doi.org/10.1515/johh-2016-0051

Mots clés
Saturation excess runoff, Infiltration excess (Hortonian) runoff, Soil erosion, Ethiopian highlands, PED model

© 2016

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Modeling sediment concentration and discharge variations in a small Ethiopian watershed with contributions from an unpaved road

Publié en ligne: 08 déc. 2016

Pages: 1 - 17

Reçu: 16 mai 2016

Accepté: 12 juil. 2016

DOI: https://doi.org/10.1515/johh-2016-0051

Mots clésSaturation excess runoff, Infiltration excess (Hortonian) runoff, Soil erosion, Ethiopian highlands, PED model

© 2016

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Mots clés
Saturation excess runoff, Infiltration excess (Hortonian) runoff, Soil erosion, Ethiopian highlands, PED model