Photo: USDA/Forest Service
SCS, 1935
Gullies in the southern US, early 20th
century
Photo: USDA/Forest Service
Gully erosion is two processes.
1. Overland flow erosion
2. Mass wasting
Photo: USDA/Forest Service
Central Iowa, Bing Bird’s Eye
SC Iowa, Bing Bird’s Eye
Rill and ephemeral gully networks feeding old perennial gullies.
Central Iowa (not on DML) : Bing Bird’s Eye
Spring gully repair before planting
Bing Birds Eye
NW Iowa
NW Iowa
Gully growth dynamics
Headcut migration rate scales
with overland flow discharge.
In stable climate and land-use,
overland flow discharge at the
headcut decreases as the headcut
migrates toward the watershed
boundary.
Thresholds
S = slope
A = upstream contributing area
Overland flow erosion dominates
where A is sufficiently large that
periodic rain/snowmelt events
exceed threshold for erosion; but
S is too small to promote
landsliding
Corollary: where A is sufficient or
gully-channel deep enough that
baseflow conditions capable of
transport are maintained
between episodes, transition to
stream channels.
Basis of the slope/area relationship
From Vandaele et al., 1996
Headcut dynamics
Robinson et al., 2000