Prior to incision spring runoff overtopped channels nearly annually. Flood waters inundated a broad floodplain, depositing a fine-textured clayey alluvium. Shrubs could not compete successfully in well-watered floodplain soils. After incision, the main channel became a 10-15 m deep arroyo. An inset fill terrace has formed within the arroyo, and is inundated infrequently.
Western wheatgrass is the dominant cover on the narrow floodplain near the bottom of the arroyo.
Incision has led to reduced plant cover. Also, plant communities have shifted in direct response to changes in soil-moisture relations induced by a changed flood regimen. Upland floodwater spreaders installed by the Bureau of Land Management are structures that attempt to replicate pre-incision hydrologic condition. The structures have temporarily and locally reversed the arroyo process by subtracting runoff and inducing deposition of alluvium in the main channel. These processes have led to an increase in forage production.