Sagamore Creek Flood Mitigation
RPS is working with Woodard and Curran on a flood mitigation study in the coastal neighborhoods adjacent to the Sagamore Creek and nearby marsh in the city of Quincy, MA. These neighborhoods have experienced nuisance flooding during rainfall events that are synchronized with high tide via surcharges through the existing storm water infrastructure. The stormdrains in the area discharge into the marsh which is connected to Sagamore Creek via a culvert that runs underneath a parking lot and upland development. Sagamore Creek connects to the Neponset River and ultimately to Dorchester Bay and therefore the marsh is subject to tidal flooding and drying as well as freshwater inputs from groundwater baseflow and storm runoff.
The present study is evaluating potential options to minimize extreme high marsh elevations that cause nuisance flooding through implementation of a tide gate in place of the culvert with various options of control protocols. The study included a short term field study to establish the existing conditions (water elevations, water temperature and water salinity), comparison of onsite data to nearby long term records, development and calibration of a model to simulate elevations in the marsh and
subsequent use of the model to assess multiple theoretical scenarios of existing and future storm, climate change, and flood control conditions. The modeling output will be used to understand the frequency of the marsh elevations above various thresholds for these scenarios. These results will be used to establish the potential reduction in nuisance flooding as well as the change in time of flooding for various areas/habitats within the marsh in order to determine if the proposed options will protect the existing species and habitat in the marsh.