Stream Restoration for Legacy Sediments at Gramies Run, Maryland: Early Lessons from Implementation, Water Quality Monitoring, and Soil Health

Katie Mattern,Marc Peipoch,Shreeram Inamdar,Alyssa Lutgen,Nathan Sienkiewicz,Jinjun Kan,Grant Jiang

doi:10.3390/w12082164

Abstract

While stream restorations are increasingly being adopted to mitigate sediment and nutrient inputs and to meet water quality regulatory targets, less information is available on the drivers behind the design, implementation, effectiveness, and cost of restorations. We address these issues for a $4.2 million stream restoration for legacy sediments implemented for a rural Piedmont stream in Maryland, USA. A total of 1668 m of stream was restored in three phases, which included the partial removal of legacy sediments, the grading of streambanks, floodplain creation, channel reshaping with meanders and pool-riffle forms, the raising of the stream bed, and the planting of riparian vegetation. The sediment, nitrogen, and phosphorus concentrations and fluxes were monitored before- and during the restoration phases. The sites selected for restoration had legacy sediments vulnerable to erosion and were on state-owned land. The restoration design was based on the need to maintain mature riparian trees and preserve existing sensitive wetland habitats. Water quality monitoring indicated that the sediment and nutrient fluxes increased during the restoration phase and were attributed to disturbance associated with construction activities and increased runoff. We also recommend that soil health needs to be included as an integral component to enhance the effectiveness and resilience of stream restorations.

Highlights

Sediment, followed by nutrients—i.e., nitrogen (N) and phosphorus (P)—are the leading causes of water quality impairment in rivers and streams in the United States [1]
Key questions that we address are: What were the key drivers, challenges, and constraints associated with site selection, design, and restoration implementation at the Gramies Run site? How did water sediment and nutrient concentrations change over the pre- and during-restoration phases of the project? How does the Gramies Run restoration compare with other studies in terms of the cost and nutrient reductions?
While water quality monitoring was performed for only the pre- and during-restoration phases, a large $4.2 million restoration for a rural stream in Maryland Piedmont provided important insights into a variety of issues associated with stream restoration

Summary

Introduction

Sediment, followed by nutrients—i.e., nitrogen (N) and phosphorus (P)—are the leading causes of water quality impairment in rivers and streams in the United States [1]. High sediment concentrations can increase water turbidity and cause harm by impeding sunlight and preventing the growth of aquatic life [2]. Sediment pollution has been attributed to upland soil erosion; recent studies suggest that valley-bottom legacy sediments [3,4,5] can contribute a substantial portion of sediment loads to streams and rivers [6,7,8,9]. Valley-bottom legacy sediment deposits, especially in the mid-Atlantic US, have been attributed to the coupled effects of ubiquitous mill dams and extensive agricultural erosion in the 17th to early 20th century [10].

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