Drivers of Sediment Accumulation and Nutrient Burial in Coastal Stormwater Detention Ponds, South Carolina, USA

Abstract

Stormwater detention ponds are widely utilized as control structures to manage runoff during storm events. These ponds also represent biogeochemical hotspots, where carbon (C) and nutrients can be processed and buried in sediments. This study quantified C and nutrient [nitrogen (N) and phosphorus (P)] sources and burial rates in 14 stormwater detention ponds representative of typical residential development in coastal South Carolina. Bulk sediment accumulation was directly correlated with catchment impervious surface coverage (R 2 = 0.90) with sediment accumulation rates ranging from 0.06 to 0.50 cm y -1 . These rates of sediment accumulation and consequent pond volume loss were lower than anticipated based on maintenance guidelines provided by the State. Nalkanes were used as biomarkers of sediment source; the derived terrestrial aquatic ratio (TAR HC ) index was strongly correlated with sediment accumulation rate (R 2 = 0.71) which, in conjunction with high C/N ratios (16-33), suggests that terrestrial biomass drives this sediment accumulation, with relatively minimal contributions from algal derived material. This is counter to expectations that were based on the high algal productivity generally observed in stormwater ponds and previous studies of natural lakes. Sediment C and nutrient concentrations were consistent among ponds, such that differences in burial rates were a simple function of bulk sediment accumulation rate. These burial rates (C: 8.7-161 g m -2 y -1 , N: 0.65-6.4 g m -2 y -1 , P: 0.238-4.13 g m -2 y -1 ) were similar to those observed in natural lake systems, but lower than those observed in reservoirs or impoundments. Though individual ponds were small in area (930-41,000 m 2 ), they are regionally abundant and, when mean burial rates are extrapolated to the regional scale (% 21,000 ponds), ultimately sequester 2.0 9 10 9 g C y -1 , Received 28 July 2017; accepted 11 November 2017; published online 16 January 2018Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-017-0207-z) contains supplementary material, which is available to authorized users. Authors' Contribution: EMS and CBN were responsible for the original conception and design of this study, with input from WFS and LAZ. Sample collection and bathymetric mapping were performed by WFS. Phosphorus analyses were performed by WFS with assistance from CBN. Carbon and nitrogen analyses were performed by WFS with assistance from EMS. N-alkane analyses were performed by WFS with assistance from LAZ. WFS, CBN, EMS, and LAZ were responsible for data interpretation. WFS drafted the manuscript and all authors contributed critical revisions. *Corresponding author; e-mail: William.Schroer@uga.edu Ecosystems (2018) 21: 1118-1138 https://doi.org/10.1007/s10021-017-0207-z Ó 2018 The Author(s). This article is an open access publication 1118 9.5 9 10 7 g N y -1 , and 3.7 9 10 7 g P y -1 in the coastal region of South Carolina alone. Stormwater ponds represent a relatively new but increasingly...

Internal loading in stormwater ponds as a phosphorus source to downstream waters

“…Stormwater ponds (hereafter, ponds) were first designed to reduce peak flows and settle out suspended solids carrying nutrients and other pollutants (Walker 1987). They have since become ubiquitous in many regions (Schroer et al 2018), making them a significant part of urban watershed hydrology and water quality management (Song et al 2015). As urban watershed nutrient management focuses largely on phosphorus (P) due to its major role in inland waterbody eutrophication, ponds are widely used to retain P (Schroer et al 2018) based on their assumed efficiency in trapping P in stormwater (Walker 1987).…”

Stormwater Ponds in the Southeastern U.S. Coastal Plain: Hydrogeology, Contaminant Fate, and the Need for a Social-Ecological Framework

“…Sedimentation in particular is an important process that protects downstream water quality, and is influenced by pond design (e.g., geometry, forebay or other installation), hydrology (e.g., retention time, potential for short-circuiting), the nature of suspended solids (e.g., allochthonous, autochthonous, and carbon or mineral composition), management activities that impact particle capture (e.g., vegetation planting/control or dredging maintenance), and even storm event-specific characteristics (e.g., hydrograph, wind speed and direction) (Greb and Bannerman, 1997;Anderson et al, 2002;Scholes et al, 2008;Vezzaro et al, 2011;Gold et al, 2017a;Moore et al, 2017). In a study of 14 stormwater wet detention ponds in coastal SC in residential urban and suburban communities, Schroer et al (2018) measured sedimentation rates spanning 0.06-0.5 cm y −1 and detected sequestration of carbon and nitrogen through burial. However, in another case study in SC, Messersmith (2007) observed a single stormwater pond lost 36% volume and the last pond in a series of 5 linked ponds lost 15% volume in 5-7 years post-construction.…”

“…These rates are dependent upon many factors, and importantly in the Southeast U.S. could be controlled by relatively low landscape erosional potentials, relatively high year-round primary production (i.e., resulting in high levels of organic debris) and continuing development pressures. For instance, rapid urbanization or development "infill" occurring in the region, and the resulting increase in impervious cover within a stormwater pond watershed, can result in increased sedimentation in ponds (Schroer et al, 2018) that could produce accelerated maintenance demands. Maintenance to dredge accumulated sediment is recommended when the pond pool volume has been significantly diminished.…”

“…This function is important for integrity of downstream structures, and ecosystems therein (Persson and Wittgren, 2003). Over time, it has been shown that ponds can serve many functions; they provide ecological habitat for birds and aquatic life (Hassall and Anderson, 2015;Greenfield et al, 2018), either trap or act as a gateway for the transport of various environmental pollutants to receiving bodies (Van Metre et al, 2000;Thapalia et al, 2010), sequester carbon (Schroer et al, 2018), provide cultural and ecosystem services (Moore and Hunt, 2012), and can serve as a valued, aesthetic feature of a community (Ghermandi and Fichtman, 2015). By averting and storing runoff on-site, ponds open up the possibility for rainwater use, such as for landscape irrigation, saltwater intrusion barriers, drinking water aquifer recharge, augmentation of potable water reservoirs, non-potable water use in buildings, and baseflow augmentation to improve freshwater habitat and recreational use depending on water quality and need (Grebel et al, 2013).…”

It Is Not Easy Being Green: Recognizing Unintended Consequences of Green Stormwater Infrastructure

“…Ponds slow and temporarily store stormwater runoff, allowing suspended solids containing the majority of stormwater contaminants to settle to the bottom of the pond from which they must be removed during infrequent maintenance [72]. If ponds are neglected, however, which is often the case [126,129], sediments, organic matter, and contaminants accumulate [130][131][132]. Under certain conditions, these contaminants may dissolve into the water and flow out of the pond [133,134].…”