The most current climate science is forecasting a 1 to 2 meter rise in sea level by 2100 (Vermeer and Rahmstorf, 2009). Regardless of the accuracy of any of the forecasts one can began to examine scenarios - how would an area flood under one sea level rise scenario versus a second. The ideal scenario might be the one that avoids inundation under both scenarios.
A common desire by managers is to view scenarios at the parcel level. There are several challenges to that end which include the resolution of the topography (USGS topo's for example typically use a 10' contours whereas FEMA's goal for flood planning are maps with a 1 to 2 foot contour interval.). There are very few tide gauges for the enormous number of coves and embayments, tidal rivers in New England and within an individual river, tidal elevations variation along a gradient as shown in the image below for the Saint Johns River.
The lack of highly accurate terrestrial lidar for low lands and highly accurate bathymetry data will impact a models ability to accurately predict the response of surge moving upstream.
Connecticut Inundation Visualization Tool:
The Connecticut Inundation Visualization Tool is made available through the Long Island Sound Array (LISICOS) of NERACOOS. Select the Coastal CT Flood Map on the index page to access this tool. Detailed elevation were collected by FEMA contractors for the extent of the 100-year coastal floodplain using LiDAR technology. This zone is narrow were the land elevation rises rapidly and widest where the land elevation rises gently. In the left hand table of contents, select coastal_DEMs and select one of the coastal regions (western, central or eastern). The following is a zoom in view to Groton in eastern CT.
|Digital elevation model, values in inches above NAVD88.|
Use the I-tool to determine the elevation at a specific location. The value returned is in inches relatived to NAVD88. This is the format the product was delivered. In this figure, the elevation for a portion of the runway at Groton-New London is 72 inches.
The challenge for inundation was which scenarios to show in a tidal environment. In western LIS where the tidal range is greatest, a 1 meter rise in sea level is less than a high spring tide. Regardless of the sea level rise scenario, that scenario is combined with a tidal flood event namely mean high water and the average maximum monthly (e.g., highest spring tides). These two scenarios would show the area of land that would be flooded twice a day or once a month respectively. So these are inundation/flooding scenarios.
|The top image shows the inundation extent at Groton-New London Airport with a 6" sea level rise during a high spring tide. The bottom images shows the same time but a sea level rise of 36 inches.|
Other scenarios that DEP is developing are for the 10-year, 50-year and 100-year tidal flood events which correspond to the flooding events associated with storms such as nor'easters and hurricanes (surge).
The purpose of the Coastal Resilience project is to provide communities with easy access to information to assist in coastal planning and management decisions regarding resources at risk from sea level rise and coastal hazards. This information is accessible through an interactive decision support tool. With the Future Scenarios Mapper, users can characterize current conditions and visualize the ecological, social and economic impacts of reasonable future flooding scenarios. Proactive solutions and adaptations can reduce impacts to human and natural communities. Appropriate planning for adaptation requires data-driven decision support, and the Coastal Resilience project provides a suite of interactive analysis options to support decision-makers.
|Snapshot of the elevation data. Select a location with I-tool and a pop-up table shows the existing elevation and then future flooding levels under various climate change scenarios.|
The future scenario mapper also provides information about shoreline vulnerability - a rating by degree of exposure or protection: