Dendrogeomorphology for Post-hoc Erosion Evaluation in Southern U.S.
Streambank erosion impacts rivers and reservoirs due to bank erosion.
However, little information of stream bank is available due to the need
for advanced planning. Dendrogeomorphology offers a post-hoc
method to calculate streambank erosion providing information about past
erosion events and processes. Bank retreat can be calculated by
dendrogeomorphology where the distance from a channel bank of an exposed
live root shows anatomical changes that are dated from the root’s growth
rings. We estimated bank erosion for three different sized southern U.S.
watersheds ranging in area from 4 to 3781 km 2 using
dendrogeomorphology compared to modeled erosion based on critical
velocity required for sediment transport. Erosion values ranging from
3.8 to 13.5 cm/yr for the smaller drainages with no difference found
between root and modeled erosion rates. The large sub-basin had erosion
ranging from 33.6 to 196.4 cm/yr with high variance associated with two
prior 2-year flow events with significant differences found between root
and modeled values. We also found distance to bank strongly and
positively correlated with root exposure in straight sections of the
channel in contrast to roots collected in meander bends attributed to
erosion processes (i.e., scour, mass wasting) occurring at these
locations. When compared with other erosion studies across the southern
U.S. prairie, our values were similar in magnitude but with low
correlation to drainage area indicating site specificity of erosion
mechanisms. We confirm dendrogeomorphology provides reasonable estimate
of bank erosion across multiple spatial scales, important for watershed
management in areas lacking intentional and persistent monitoring.