Participatory and Spatial Analyses of Environmental Justice Communities' Concerns about a Proposed Storm Surge and Flood Protection Seawall.

In response to increasing threats from sea-level rise and storm surge, the City of Charleston, South Carolina, and the US Army Corps of Engineers (USACE) propose constructing a seawall around the Charleston peninsula. The proposed seawall will terminate close to lower wealth, predominantly minority communities. These communities are identified as environmental justice (EJ) communities due to their history of inequitable burdens of industrial and urban pollution and proximity to highways and US Environmental Protection Agency (EPA) designated Superfund sites. The present study documents community concerns and opinions related to the proposed seawall, existing flooding problems, and other issues. The project was guided by knowledge co-production and participant-observation approaches and included interviews with community members, collection of locality-specific data, GIS mapping to visualize key issues, development of an ArcGIS Story Map, and participation in public meetings. Community concerns are reported in the voices of community members and fell into eight major themes: community connections, drainage, impacts of road infrastructure, displacement, increasing vulnerability, sense of exclusion and isolation, mistrust of government, and civic engagement. Community members were significantly engaged in the study and are the owners of the results. As one of the first US East Coast cities pursuing major structural adaptation for flooding, Charleston is likely to become a model for other cities considering waterfront protection measures. We demonstrate the importance of meaningful engagement to ensure that climate adaptation will benefit all, including marginalized communities, and have as few unintended negative consequences as possible. Bringing more people to the table and creating vibrant, long-term partnerships between academic institutions and community-based organizations that include robust links to governmental organizations should be among the first steps in building inclusive, equitable, and climate resilient cities.

Flood-induced transport of PAHs from streambed coal tar deposits.

We assessed whether coal tar present in contaminated streambed sediments can be mobilized by flood events and be re-deposited in an adjacent floodplain. The study was conducted within a contaminated urban stream where coal tar wastes were released into a 4-km reach from a coke plant in Chattanooga, Tennessee, USA. Sediments containing visible amounts of coal tar were dredged from the streambed in 1997-98 and 2007 as part of a cleanup effort. However, post-dredging sampling indicated that very high concentrations of polycyclic aromatic hydrocarbons (PAHs) remained in streambed sediments. Sampling of sediments in the floodplain at two sites downstream of the coke plant indicated that high concentrations of PAHs were also present in the floodplain, even though no coal tar was observed in the samples. Age-dating of the floodplain sediments using 137Cs indicated that peak PAH concentrations were contemporary with coke plant operations. While there was little or any direct contamination of the floodplain sediments by coal tar, sediment contamination was likely a result of deposition of suspended streambed sediments containing sorbed PAHs. A flood model developed to delineate the extent of flooding in various flood recurrence scenarios confirmed the potential for contaminated streambed sediments to be transported into the adjacent floodplain. It was hypothesized that coal tar, which was visibly "sticky" during dredging-based stream cleanup, may act as a binding agent for streambed sediments, decreasing mobility and transport in the stream. Therefore, coal tar is likely to remain a persistent contaminant source for downstream reaches of the stream and the adjacent floodplain during flood events. This study also showed that even after excavation of tar-rich streambed sediments, PAH contaminated non-tarry sediments may be a source of flood-related contamination in the adjacent flood plain. A conceptual framework was developed to delineate specific mechanisms that can mobilize contamination from stream sources.

Assessing potential removal of low-head dams in urban settings: an example from the Ottawa River, NW Ohio.

This is a study of the scientific component of an effort to restore an urban river by removing a low-head dam. The Secor Dam is owned by a local government entity near Toledo, Ohio. The proposed removal of the last structure impeding flow on the Ottawa River has broad appeal, but the owner is concerned about liability issues, particularly potential changes to the flood regime, the presence of contaminated sediments behind the dam, and possible downstream transport of reservoir sediments. Assessing sediment contamination involved sediment sampling and analysis of trace metals and organic contaminants. Forecasting sediment transport involved field methods to determine the volume and textural properties of reservoir and upstream sediment and calculations to determine the fate of reservoir sediments. Forecasting changes in the flood regime involved HEC-RAS hydrological models to determine before and after dam removal flood scenarios using LiDAR data imported into an ArcGIS database. The resulting assessment found potential sediment contamination to be minor, and modeling showed that the removal of the dam would have minimal impacts on sediment transport and flood hazards. Based on the assessment, the removal of the dam has been approved by its owners.