Quantifying Effectiveness of Streambank Stabilization Practices on Cedar River, Nebraska

Abstract

Excessive sediment is a major pollutant to surface waters worldwide. In some watersheds, streambanks are a significant source of this sediment, leading to the expenditure of billions of dollars in stabilization projects. Although costly streambank stabilization projects have been implemented worldwide, long-term monitoring to quantify their success is lacking. There is a critical need to document the long-term success of streambank restoration projects. The objectives of this research were to (1) quantify streambank retreat before and after the stabilization of 18 streambanks on the Cedar River in North Central Nebraska, USA; (2) assess the impact of a large flood event; and (3) determine the most cost-efficient stabilization practice. The stabilized streambanks included jetties (10), rock-toe protection (1), slope reduction/gravel bank (1), a retaining wall (1), rock vanes (2), and tree revetments (3). Streambank retreat and accumulation were quantified using aerial images from 1993 to 2016. Though streambank retreat has been significant throughout the study period, a breached dam in 2010 caused major flooding and streambank erosion on the Cedar River. This large-scale flood enabled us to quantify the effect of one extreme event and evaluate the effectiveness of the stabilized streambanks. With a 70% success rate, jetties were the most cost-efficient practice and yielded the most deposition. If minimal risk is unacceptable, a more costly yet immobile practice such as a gravel bank or retaining wall is recommended.

Impact of Bank Stabilization Structures on Upstream and Downstream Bank Mobilization at Cedar River, Nebraska

“…Its streambanks have been stabilized, successfully or unsuccessfully, with various techniques over a period of many decades. Two previous studies conducted on the Cedar River evaluated the effectiveness of streambank stabilization structures on streambank erosion and deposition (Dave and Mittelstet, 2017;Russell et al, 2021). Dave and Mittelstet (2017) quantified the streambank retreat before (0.45 m 2 m -1 year -1 ) and after (0.16 m 2 m -1 year -1 ) the stabilization of 18 streambanks.…”

“…Two previous studies conducted on the Cedar River evaluated the effectiveness of streambank stabilization structures on streambank erosion and deposition (Dave and Mittelstet, 2017;Russell et al, 2021). Dave and Mittelstet (2017) quantified the streambank retreat before (0.45 m 2 m -1 year -1 ) and after (0.16 m 2 m -1 year -1 ) the stabilization of 18 streambanks. They found that the stabilized banks were more efficient than the control sites at reducing erosion.…”

Impact of an Extreme Flood Event on Streambank Retreat: Cedar River, Nebraska, USA

“…From 2000 to 2005, streambank stabilization projects were implemented to reduce streambank erosion and improve surface water quality. Through the Cedar River Stabilization Project, 20 streambanks were stabilized using six different techniques, predominantly wooden log jetties, along the river, of which four were constructed between Ericson Dam and Spalding Dam (Dave and Mittelstet 2017).…”

Streambank Erosion: Advances in Monitoring, Modeling and Management

“…The research articles included in this special issue specifically targeted three areas that are key to better understanding streambank erosion and failure, namely, monitoring [8][9][10][11], modeling [12][13][14][15][16][17], and management [18][19][20][21]. As an ensemble, the articles highlight the value of monitoring campaigns to characterize the effect of external drivers (e.g., hydrologic events), the capabilities and limitations of numerical models for predicting the response of the system (e.g., stream restoration design), and the effectiveness of management practices to prevent and mitigate the impacts of streambank erosion and failure.…”

“…Dave and Mittelstet [20] evaluated the effectiveness of six stabilization practices (e.g., jetties, rock vanes) that were implemented across 18 different bank locations. They used aerial imagery to quantify pre-and post-stabilization bank retreat and to assess the impact of a major storm event that took place during the evaluation period.…”