Water quality assessment of stream restoration for legacy sediments at Gramies Run, Maryland
Date
2020
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Publisher
University of Delaware
Abstract
Streambank legacy sediments are an important contributor to sediment and nutrient pollution in the mid-Atlantic region of the United States. Stream and floodplain restoration projects are increasingly being adopted to reduce this pollution with investments in the millions to billions of dollars. While many of these projects target reductions in sediments and nutrients to meet TMDL goals, very few of these projects include any water quality monitoring to assess their effectiveness. ☐ This study examines the water quality effects of a more than $4.2 million stream restoration project on Gramies Run, in Cecil County, Maryland, USA. As part of the restoration, streambanks were graded, in-stream features were added, and riparian vegetation was planted. Water quality monitoring was performed for approximately 9 months pre-restoration and 15 months during restoration, upstream and downstream of the restoration reaches. Sampling included measurements of streamflow, temperature and turbidity, as well as grab water sample collection during non-stormflow and stormflow periods to estimate nitrate-N, TN, DOC, and ortho-P concentrations and fluxes. Nitrate-N, TN, and DOC flux increased significantly during the restoration period at the downstream monitoring site. Additionally, sediment flux almost doubled at the downstream site during the restoration. These increases were attributed to disturbances associated with restoration as well as greater mobilization and transport of sediment and nutrients due to increased precipitation and runoff during the restoration phase. These results highlight the importance and need of conducting water quality monitoring for such stream restorations. While this study did not include any post restoration monitoring, monitoring is recommended for a minimum of five years to assess the recovery of the site following the restoration. A quick cost analysis revealed that this restoration project was more expensive (on a per linear foot basis) than others evaluated.
Description
Keywords
Streambank legacy sediments, Sediment pollution, United States, Maryland, Restoration