Flood Mitigation in the Chesapeake Beach SeaGate Community

Abstract

The town of Chesapeake Beach is on the Chesapeake Bay’s western shore and is directly connected to the Bay by creeks that feed tidal marshes. Marshland within Chesapeake Beach’s South Creek Estuary was filled in to enable community development, including the SeaGate townhouse community and Maryland Route 261. At less than four feet above mean sea level, Route 261 and the SeaGate’s parking lots flood during high tide events, storm swells, and intense storm events. In addition to being inconvenient for community members, it is also a safety concern as Route 261 provides access to the SeaGate community, the local fire department, and wastewater treatment plant.The historical practice of filling in wetlands for development and the increasing pressures of climate change have resulted in worsening flooding in the SeaGate community. Chesapeake Beach’s 2021 Comprehensive Plan discusses the area’s future of coastal resiliency and mentions the need to create a coordinated and consistent plan for addressing sea level rise. There have been previous attempts by the community to control flooding resulting from rising tides and stormwater. The Army Corps of Engineers installed revetments and a gate to control tidal fluctuations, and the Maryland State Highway Administration raised Route 261 to prevent the road from flooding. However, the floodgate is no longer operational and mounting pressures from sea level rise combined with more intense storms have flooded the road with increasing frequency. This report’s proposed solutions address both tidal and stormwater flooding. Because the primary source of flooding is from the Chesapeake Bay, the floodgate must be replaced. The new floodgate will be automated to be in sync with tidal cycles and local weather conditions. The gate will automatically close at high tide and open at low tide to allow for the migration of wildlife between the tidal marshes and the Chesapeake Bay. There will also be an option to manually open and close the gate at the SeaGate community’s discretion. As well, three different technologies will address stormwater flooding—cisterns, permeable pavers, and bioretention cells. Cisterns will be fitted to the townhouse units to store runoff from rooftops. They will be sized to capture a five-year, 24-hour storm (4.18 inches), but can be adjusted to capture the runoff from various storms. The captured water will be automatically released during dry periods and at low tides, as controlled by a smart system, however there will also be a manual option to give community members more control. Permeable pavers will reduce the volume of runoff and allow more water to infiltrate into the soil. They will be placed in low-traffic areas, such as parking lots and sidewalks, to reduce the wear on the pavers and extend their lifetime. Bioretention cells will be implemented alongside roads and parking lots to help manage runoff volume and quality. There are a few existing bioretention cells in the SeaGate community, but they aren’t maintained and don’t appear to function well. The proposed design improves the existing systems and adds new bioretention cells. To increase the feasibility of the proposed solutions and minimize the burden on the community, the report recommends applying to grant programs intended to help fund climate resiliency and sustainability projects in Maryland. Some of these include the Chesapeake and Coastal Grants Gateway, the Maryland G3 Grant Program, and the Watershed Assistance Grant Program. These grants will help fund the proposed solutions and create a safer, more climate resilient Seagate community.