Streambank erosion is an important contributor to sediment
and nutrient export. This study determined total P (TP), soil-test
P (Modified Morgan’s, MM-P), and the degree of P saturation
(DPS) in eroding riparian soils along four Lake Champlain Basin
stream corridors. We investigated the relationship between these
data and soil texture and with a series of GIS-derived landscape
metrics. We also quantified the potential P load from eroding
streambanks using remote sensing. Soil samples were taken
from 76 erosion features to a depth of 90 cm on four streams
in Chittenden County, Vermont. Mean concentrations of TP and
MM-P were similar among the watersheds and through depth.
Neither TP, MM-P, nor DPS were well related to texture. Metrics
from available spatial databases for parent material, soil series,
and landscape position were somewhat useful in predicting TP
and MM-P. Eroding streambank soil from 2004 through 2007 in
the four streams was estimated to contain from 0.5 to 3.9 Mg of
TP and 1.4 to 10.9 kg MM-P. The mean DPS in each watershed
was <18% and, along with low MM-P concentrations, suggests
that eroded streambanks may act as sinks rather than sources of
P. The portion of total nonpoint P export potentially contributed
by streambank erosion ranged from 6% in the stream with the
lowest erosion rate to 30% in the stream with the highest erosion
rate. Based on TP values, the P contribution of these streambanks
could be considerable, and more information is needed on their
actual contribution to bioavailable P in receiving waters.