Streambank erosion over time and space
Date
2023-05
Authors
Allen, Jade
Major Professor
Advisor
Moore, Peter
Isenhart, Thomas
Miller, Bradley
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Sediment supplied from streambank erosion is a potentially significant contributor to the phosphorus (P) load in Iowa rivers and streams. Streambank stabilization structures have been installed in Iowa rivers to reduce the bank recession compromising infrastructure and valuable land, with growing interest in stabilization as a possible nutrient reduction strategy. Efforts to better target, quantify, and mitigate excessive streambank erosion are of high priority at the state level to meet nutrient reduction goals. However, most studies on bank erosion are limited in spatial and temporal extent, leading to an inability to properly estimate contributions of sediment and phosphorus (P) from streambank erosion. Further, despite the widespread installation of streambank stabilization and flow-training structures, only some studies consider the effects of these structures on erosion and deposition over time and at various scales. In confronting these two major shortcomings in current river management, two studies spanning two watersheds and using two methods of analyzing streambank erosion were performed. In the first study, an erosion pin dataset spanning ten years with pinned banks spread across a 3rd order watershed was analyzed alongside the hydrologic record to assess hydroclimatic effects on recession rates and estimate sediment inputs from bank erosion. Results indicate an estimated 30,238 Mg of sediment and 11 Mg of P were introduced in Onion Creek from streambank erosion with a range in recession rates from 4.2 to 19.4 cm per year. In the second study, streambanks with stabilization structures were analyzed alongside actively meandering streambanks at the scale of a structure, meander bend, and river reach of a 6th order watershed. Effects on erosion and deposition were assessed using aerial change detection using the Aerial Imagery Migration Model (AIMM) and controlling for radius of curvature. Results at the point and bend scale over six years show a reduction in mean local migration rates and a significant reduction in depositional and erosional area in stabilized bends. The reach with several stabilization structures showed a slight reduction in the average linear erosion rate but a dramatic increase in the deposition rate and increased deposition downstream from and between stabilized banks. These findings highlight the importance of quantifying both erosion and deposition in evaluating bank stabilization as a tool for sediment and nutrient control.
Series Number
Journal Issue
Is Version Of
Versions
Series
Academic or Administrative Unit
Type
thesis