Soil Erosion
Ephemeral Gully Erosion
Ephemeral gullies are small channels of eroded soil that form in unprotected soils (such as cropland and construction sites) during rainfall events. Ephemeral gullies often form in the same place every year and add to producer's management time and cost. Ephemeral gullies can be removed by tillage. Ephemeral gully erosion often exceeds losses from other upland sediment sources, but little is known about how effective various practices are in reducing ephemeral gully erosion.
Ephemeral gullies are studied in our group from different perspectives, such as field studies, geospatial and numerical modelling, and laboratory soil analysis.
Field Studies
An agricultural field with developed network of ephemeral channels and headcut gullies was instrumented to measure gully geometry, precipitation, soil moisture and runoff. The collected data were used to assess the impacts of measured factors on ephemeral gully development. Ephemeral gully geometry was measured with a custom-made pin-frame apparatus with vertical accuracy of 5 mm.
Geospatial/Physical Modeling
Topographic Index (TI) Models
Topographic index models represent combinations of primary topographic attributes evaluated at every point (GIS pixel). For every pixel, if index exceeds a specified threshold value, the gully must form.
|
Model |
Index |
Description |
|
CTI |
CTI = A·S·C |
Compound topographic index |
|
WTI |
WET = log(A/S) |
Topographic wetness index |
|
SA |
SA = A·S |
Stream power index |
|
SAP |
CIT = S·Ab,0<b<1 |
Channel initiation index |
A is the upstream drainage area, S is the local slope, C is the planar curvature.