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Conceptual Soil Erosion Model

Preferential flow

Erosion Research Areas:

After half a century of study, soil erosion continues to be a serious global problem and substantial controversy persists regarding the underlying mechanisms and processes. We have active and on-going research in soil erosion and related processes across many scales from the impact of a raindrop to soil plots, fields, rivers, watersheds and regions. Two examples of research areas that characterize the breadth of scales are:

  • Raindrop-soil surface interactions
  • Climate and land use change impacts on Ethiopian Highland soil erosion

Raindrop-soil surface interactions

It is widely recognized that upland erosion is largely initiated by the impact of raindrops on the soil surface. We have used a simple experimental design to investigate the interactions between soil and raindrops. One of our notable discoveries was the development of a “shield” over the original soil that protects the underlying soil from unfettered erosion. This figure is a sequence of photographs showing the development of the shield (dark sand layer at the surface) and the associated changes in sediment concentrations in the runoff; notice that the ponded runoff is clear at the end of the experiment even though rain is continuing. These results confirm one of the important underpinning processes of the Rose erosion model (Hairsine and Rose, 1991; Rose et al., 1994). This experiment has been used to investigate the roles of infiltration and surface ponding on erosion as well. We also recognize that the depth of the shield shows how deeply raindrops penetrate the soil surface, which is allowing us to develop new theories and models describing how solutes, bacteria, and other substances are transferred from soil into runoff.

Soil and Water Lab people working on this project: Sara Storrer

Principal Investigator: Todd Walter

Funding Source:

Climate and land use change impacts on Ethiopian Highland soil erosion

Ethiopia has been a hot spot for erosion, ironically, due to both too much rainfall in and severe drought. During the 1970s and 1980s soil and water conservation practices were widely implemented. However, success was much lower than expected and, in some places, it was a complete failure. Our research has been tailored to alleviate impacts of erosion both in Ethiopia and throughout the Nile basin. Using monitored watersheds and plot experiments we have discovered, counter intuitively, that flat parts of the landscape are primary sediment sources. We have used our improved understanding of the regional erosion processes to develop models and map erosion risks. On-going work is focusing on lake sedimentation, rill and gully formation, improved soil and water conservation practices.

Active land degradation as a result of erosion in Northern Ethiopia

Soil and Water Lab people working on this project: Christian Guzman, Haimanote Bayabil, and Tigist Tebebu

Principal Investigator: Tammo Steenhuis