Impact of an Extreme Storm Event on River Corridor Bank Erosion and Phosphorus Mobilization in a Mountainous Watershed in the Northeastern United States

Abstract

Movement of sediment, and associated phosphorus, from stream banks to freshwater lakes is predicted to increase with greater frequency of extreme precipitation events. This higher phosphorus load may accelerate harmful algal blooms in affected water bodies, such as Lake Champlain in Vermont, New York, and Québec. In the Mad River, a subwatershed in central Vermont's Lake Champlain Basin, extreme flooding from Tropical Storm Irene in 2011 caused extensive erosion. We measured stream channel change along the main stem between 2008 and 2011 by digitizing available prestorm and poststorm aerial imagery. Soils were sampled post Irene at six active stream erosion sites, using an experimental design to measure differences in soil texture and phosphorus both with depth (90 cm) and distance from the stream. In addition to total phosphorus (TP), we determined bioavailable (soil test) phosphorus (STP) and the degree of phosphorus saturation (DPS). The six sites represented a 0.87‐km length of stream bank that contributed an estimated 17.6 × 103 Mg of sediment and 15.8 Mg of TP, roughly the same as average annual watershed export estimates. At four sites, the STP and DPS were low and suggested little potential for short‐term phosphorus release. At two agricultural sites where the lateral extent of erosion was high, imagery showed a clear loss of well‐established riparian buffer. Present‐day near‐stream soils were elevated in STP and DPS. An increase in these extreme events will clearly increase sediment loads. There will also be increasing concentration of sediment phosphorus if stream banks continue to erode into actively managed agricultural fields.

Spatio-seasonal variation of water quality influenced by land use and land cover in Lake Muhazi

“…2 ) are higher in dry season which may be justified by relatively more farming activities executed around the area moving into the lake as runoff. Soil erosion that occurs during floods takes away these parameters from adjacent land and the river banks into the water bodies 77 , 78 . Cropland influence is explained by inappropriate use of inputs, mostly chemical fertilizers specifically urea, and NPK that is hugely used in the study area.…”

Soil Amended With Organic Matter Increases Fluvial Erosion Resistance of Cohesive Streambank Soil

“…Broadly, climate change may exacerbate streambank erosion and channel migration in part due to changes in environmental conditions such as water and soil temperature (Hoomehr et al., 2018; Nelson & Palmer, 2007) and storm frequency/intensity (Ross et al., 2019). Bank erodibility can have significant impacts on channel morphology, including meander morphology (Bogoni et al., 2017) and channel form (Fernandez et al., 2021).…”

Terrain‐derived measures for basin conservation and restoration planning

“…To illustrate our framework, we chose the Mad River watershed located in central Vermont (Figure 1), due to the abundance of prior work related to stream geomorphic conditions and processes (Ross et al, 2019; Worley et al, 2023) and the availability of a well‐calibrated 2D HEC‐RAS model for assessing our low‐complexity model results (Seigel, 2021; Worley et al, 2022). Elevations in the Mad River watershed range from 132 to 1245 m above sea level.…”