Aerial Assessment of Ephemeral Gully Erosion from Agricultural Regions in the Pacific Northwest

Soil erosion from agricultural areas continues to be problematic in terms of both financial and environmental measures. Ephemeral gullies contribute to the soil loss both by the volume of sediment eroded from the gullies and because they act as delivery channels for surface erosion. High resolution aerial imagery was used to quantify the amounts and locations of ephemeral gullies in the subbasins of the Potlatch River system. Areal ephemeral gully erosion rates varied from 33.6 mt/km(2) (0.15 U.S. t/acre) in the Big Bear Creek Subbasin to 88.4 mt/km(2) (0.39 U.S. t/acre) in the Middle Potlatch Creek Subbasin representing 2.3-7.7% of the total surface sediment load. An erosion potential index was proposed to assist resource managers predict gully locations at the watershed scale using readily available remote sensing and geographic information system layers.