Impact of road building on gully erosion risk: a case study from the Northern Ethiopian Highlands

作者：Jan Nyssen, Jean Poesen, Jan Moeyersons, Edith Luyten, Maude Veyret‐Picot, Jozef Deckers, Mitiku Tefera Haile, Gérard Govers · 发表于：Earth Surface Processes and Landforms · 年份：2002 · DOI：10.1002/esp.404 · 被引用次数：255 · 研究领域：Soil erosion and sediment transport、Hydrology and Sediment Transport Processes、Hydrology and Watershed Management Studies

Abstract Although obvious in the field, the impact of road building on hydrology and gullying in Ethiopia has rarely been analysed. This study investigates how road building in the Ethiopian Highlands affects the gully erosion risk. The road between Makalle and Adwa in the highlands of Tigray (northern Ethiopia), built in 1993–1994, caused gullying at most of the culverts and other road drains. While damage by runoff to the road itself remains limited, off‐site effects are very important. Since the building of the road, nine new gullies were created immediately downslope of the studied road segment (6·5 km long) and seven other gullies at a distance between 100 and 500 m more downslope. The road induces a concentration of surface runoff, a diversion of concentrated runoff to other catchments, and an increase in catchment size, which are the main causes for gully development after road building. Topographic thresholds for gully formation are determined in terms of slope gradient of the soil surface at the gully head and catchment area. The influence of road building on both the variation of these thresholds and the modification of the drainage pattern is analysed. The slope gradient of the soil surface at the gully heads which were induced by the road varies between 0·06 and 0·42 m m −1 (average 0·15 m m −1 ), whereas gully heads without influence of the road have slope gradients between 0·09 and 0·52 m m −1 (average 0·25 m m −1 ). Road building disturbed the equilibrium in th...