Rerouting water: Understanding and managing urban hydrology in historic Charleston
Published:March 21, 2019
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C. Guinn Wallover, Timothy J. Callahan, Amy E. Scaroni, Kimberly Counts Morganello, 2019. "Rerouting water: Understanding and managing urban hydrology in historic Charleston", Field Excursions in the Carolinas: Guides for the 2019 GSA Southeastern Section Meeting, John Chadwick, Steven C. Jaume’
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The built environment of peninsular Charleston, South Carolina, has been strongly influenced by the ethos of architectural preservation. However, increased frequency of storm and tide-related flooding has been affecting property and public services, and threatens human and environmental health. Management processes for excess water in this urban area must adapt to the challenges resulting from historic development including the fill of tidal creek systems, sea-level rise, and the influence of large storm events on drainage infrastructure. The City of Charleston has adopted several strategies to manage flooding and encourage progressive development. Large-scale drainage improvement projects capitalize on a geologic framework that provides for deep tunnel excavation and drainage system construction. Novel approaches in zoning codes provide some incentives for land owners to use lower impact design techniques in return for more flexible design standards. This field tour will guide participants through this historic city, and will provide a glimpse of the geologic setting, development history, and environmental pressures that have compelled the city’s proactive stormwater management.
Traditionally, urban stormwater management focused on creating and maintaining drainage infrastructure. The U.S. Environmental Protection Agency (USEPA) National Pollutant Discharge Elimination System (NPDES) provides regulatory oversight and guidance to municipalities on point sources and nonpoint sources of water-based pollution to receiving water bodies; stormwater is one of several vectors of concern (https://www.epa.gov/npdes/npdes-stormwater-program). Within the past few decades, the concepts of green infrastructure (GI) and low impact development (LID) have garnered more attention because of various benefits to reducing stormwater runoff, and related water quality impairments through mimicking natural biogeochemical processes (Ellis et al., 2014). The USEPA as well as state and local government agencies have promoted GI and LID practices to the public (real estate developers and landowners) through various incentives. Architectural review committees are addressing the desire for landowners to implement GI and LID techniques where restrictions or covenants may legally prevent such practices. This field trip in historic Charleston, South Carolina, will provide a context for historic and modern-day flood concerns on the peninsula, as well as highlight solutions for increasing community resilience to flood-waters and stormwater runoff through the lens of architectural and historical preservation.
A website has been created as a supplement for this 2019 field trip; see https://scgis.maps.arcgis.com/apps/MapSeries/index.html?appid=7645e6ef78514c60b43610865c4502e4.
See Figure 1 for a map of field-trip stops.
Stop 1: Joe Riley Waterfront Park, Intersection of Boyces Wharf and Concord Street, Charleston, SC 29401 (Coordinates: 32.778916° N, 79.925479° W)
Participants will begin the field trip with a panoramic view of the Charleston Harbor (Fig. 2). The Charleston peninsular area is dominated by Pleistocene- to modern-age barrier-island quartz sand facies, tidal-marsh organic-rich clay and sand deposits, and artificial fill and a series of small, tidal marsh creek systems (Weems et al., 2014). Peninsular Charleston is located between the Ashley and Cooper Rivers, tidal systems with relatively small natural watersheds. These river basins cumulatively drain 1737 square miles of forested lands, wetland and open water, and an expanding footprint of urban and suburban developed landscapes (SCDHEC, 2018). The Charleston Harbor, at the mouth of the Cooper River, is managed to provide for a large port system, considered the seventh highest U.S. port for ocean imports (Descartes, 2018). The port supports foreign and domestic container services, as well as an evolving tourism industry that serves as a port of call for multiple cruise lines.
Stop 2: Water Street and Church Street, 44 Church Street, Charleston, SC 29401 (Coordinates: 32.773098° N, 79.929299° W)
At the next stop, participants will explore the historic area of Charleston. Initial development in the peninsula occurred along the high land running down the “spine” of the city. Historically, development pressures resulted in the fill of many low-lying creek systems, allowing for community expansion. Other modifications to creek systems included the creation of impoundments, through damming, to support rice and sawmill industries. These types of modifications are no more evident than at historic Water Street, now a paved and cobblestoned residential road. This was formerly a confluence of two small tidal creeks, Major Daniels and Vanderhorst Creeks, which bisected the southerly tip of the peninsula (Fig. 3). Historic maps of the Charleston peninsula (Figs. 3 and 4) show city development between 1780 and 1890, and the location of former tidal creek systems that were subsequently filled as growth progressed. At this stop, participants can view examples of historic development and “made land” (fill) practices that, paired with Charleston’s low-lying topography and the influence of sea-level rise, have contributed to increased frequency of flooding concerns throughout the peninsula. Compression of fill material, including decomposition of organic material, leads to slumping and needed maintenance of infrastructure. Since 1995, the incidence of “sunny day” flooding from tides has increased dramatically from ~14 days per year to 50 days in 2016 (Sweet et al., 2017). This historical context sets the stage for Stops 3 and 4, where participants will explore how municipalities and builders in the Charleston region are working to manage flooding and prepare for future challenges posed by climate change.
Stop 3: Charleston Maritime Center, 10 Wharfside Street, Charleston, SC 29401 (Coordinates: 32.788897° N, 79.925135° W)
At the third stop, participants will visit the site of the Charleston Maritime Center, where a pump station is located and stormwater outfalls to the Cooper River as part of the City of Charleston’s Market Street Drainage Improvement Project. Historic Market Street, built on a former tidal creek bed, is a tourism focal point of the city and approximately one kilometer south of the Maritime Center. Locally, Market Street is also known as a location of flooding during storm events. Beginning in 2006, the City of Charleston began a multi-phase project to improve drainage in and around the Market Street basin. Construction has included a 50-m-deep tunnel system in the Ashley Formation, a wet well, and a pump station, which discharges water to the Charleston Harbor near the Charleston Maritime Center (Fig. 5). A 3.5-m-diameter stormwater tunnel lies within the silty-sand to silty-clay calcareous Ashley Formation (locally referred to as “Cooper Marl” [Malde, 1959]) of early Oligocene age that is massive and smooth-textured, allowing for relatively safe tunnel construction. Future phases of the Market Street project include improvements for a redesigned surface drainage system and streetscape project. More information on the Market Street Drainage Improvement Project can be found on the City of Charleston’s website (https://www.charleston-sc.gov/index.aspx?nid=591; accessed 18 January 2019).
Stop 4: The Workshop, 1505 Monrovia Street, Charleston, SC 29405 (Coordinates: 32.817366° N, 79.952053° W)
The last stop on the field trip is a publicly accessible redevelopment project that is part of the City of Charleston’s Upper Peninsula Initiative. This project and the zoning board seek to promote the use of sustainable development practices, including low impact development (LID) for stormwater management, through development incentives. The Workshop, a former industrial site, has incorporated permeable pavement and multiple bioretention cells into site design. Design and city staff worked collaboratively to overcome barriers for LID use, including concerns for incorporation of infiltration practices in industry-related remnant soil contaminant sites (Figs. 6 and 7). The Workshop provides a case study of the efforts of the city to encourage progressive design practices to meet the evolving challenges of stormwater management in Charleston.
This field trip highlights the complex nature of stormwater management in the urban setting of historic peninsular Charleston, South Carolina. Examples of projects, such as the Market Street Drainage Improvement Project and The Workshop, showcase some of the mitigation approaches that include traditional, large-scale engineering efforts, as well as novel low-impact development building practices that are required to meet the challenges of tourism, economic, and climate change in this growing coastal city.
Figures & Tables
Field Excursions in the Carolinas: Guides for the 2019 GSA Southeastern Section Meeting
This guidebook provides detailed itineraries of three field trips associated with the 2019 GSA Southeastern Section Meeting in Charleston, South Carolina. The first chapter outlines the fossiliferous deposits near Charleston historically referred to as the “Ashley Phosphate Beds,” which include sharks, rays, sea turtles, whales, and other Oligocene to Pleistocene fossils. The second chapter explores how hydrology has shaped Charleston and how engineers, public officials, and citizens incorporate new technologies in design to increase community resiliency. The third chapter describes the variety of modern traces that can be observed in the coastal setting of Edisto Island near Charleston. These include burrows, tracks, borings, and other signs of terrestrial and marginal-marine invertebrates and vertebrates in sediments, shells, and wood.
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- Charleston South Carolina
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