Full Text
Salem Flood Map Revisions Sean W. Kelley, P.E. Applied Coastal Research and Engineering [PHONE REDACTED] www.appliedcoastal.com ---PAGE BREAK--- Some Useful Definitions • Wave Setup – water level increase along a shoreline due to wave breaking in the surf zone • Wave Run Up ‐ uprush of water from wave action on a shore barrier • Wave Overtopping – flow of water over a shore barrier from waves • Storm Surge – Increase in water level due to meteorological effects (winds and barometric pressure) • 100‐year Storm – an event with a 1% chance of occurring or being exceeded in any given year Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Some More Useful Definitions • Flood Insurance Study (FIS) – FEMA analysis that is the basis of the flood map delineation • LOMR – Letter of Map Revision • Base Flood Elevation (BFE) – total hazard area elevation which includes all effects from storm surge, setup, run up and overtopping • Zone VE – Coastal flood zone with velocity hazard from waves greater than 3 feet • Zone AE ‐ Coastal flood zone with waves component less than 3 feet • Zone AO – Flood Depths of 1 to 3 feet from sheet flow on sloping terrain Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Opportunities for Mapping Improvements • Site specific analysis of offshore waves – Directional analysis of waves – Determine impact of wave sheltering by islands, ledges and shoals that bound Salem Sound – Alternate Setup determination • Reanalysis of offshore storm surge levels • Improve resolution of FIS analysis – Account for variable nature of shoreline – Add new analysis transects Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Where Improvements are Possible Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Analysis of Waves Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- SWAN Model of Salem Sound Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Simulation of 1% East conditions Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Analysis Transects Used to Delineate Flood Zones Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Summary of Proposed Changes • Juniper Point & Winter Island – Lower VE zone elev. (21 ft reduced to 16 ft NAVD) – Reduce VE zone extent – Lower AE zone elev. (14 ft reduced to 11 ft NAVD) – Expanded zone X (out of 1% floodplain) • South Salem & Forest River – Lower AE zone elev. (11ft reduced to 10 ft NAVD) – Reduced area of AE zone. Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- Sept 19, 2016 Applied Coastal Research and Engineering, Mashpee, MA ---PAGE BREAK--- ---PAGE BREAK--- ---PAGE BREAK---