Loading...
HomeMy WebLinkAboutPublic Shoreline Management Alternatives_201401231559377527Public Shoreline Management Alternatives Rebecca Haney Coastal Geologist Massachusetts Office of Coastal Zone Management Coastal Management Challenge •Balance protection of natural resource function with human use. Coastal Management Needs Analysis •What is the goal? •What are the causes of erosion/damage? –Tides –Waves –Currents •Options to address causes? –Upland Runoff? –Vegetative Stabilization? –Reconfigure uses? –Need for stabilization? •Impacts •Benefits •Costs Shore Parallel Structures •Erosion continues •Cuts off sediment source •Causes end scour •Causes increased erosion •Can be overtopped •Requires monitoring •Requires mitigation •Costly to maintain End Effects of Walls Shore Perpendicular Structures •Constructed with rock, wood, concrete or sandbags •Design minimum length, width and height necessary •Traps sediment moving alongshore •Starves downdrift beaches, unless filled to entrapment •Reflects wave energy •Can have rip currents adjacent to them •Reduces erosion of beach nourishment projects •Requires monitoring •Requires maintenance to keep filled to entrapment Offshore Breakwaters •May reduce local erosion rate •Interrupts longshore transport of sediment •Used with beach nourishment •Requires monitoring Sand-filled bags •Stops erosion of sediment source •Reflects wave energy •May be marine debris hazard •End effects •Vegetation often can’t establish in them. •Requires monitoring and maintenance. Bioengineering: Coir Rolls & Vegetation Before During Construction 10 Years later • Reflects less wave energy than rocks or sandbags •Limits erosion of sediment sources •Can be used to re- establish vegetation Bioengineering – Natural Fiber Blankets •Blankets stabilize soils while vegetation gets established •Use in conjunction with coir rolls and vegetation •Do not use synthetic fibers Nourishment •Add sediment to the beach, dune, or nearshore to enhance natural storm damage protection system. •Requires monitoring. •Beach Nourishment: Mass DEP’s Guide to Best Management Practices for Beach Nourishment in MA (2007). Dune Nourishment & Artificial Dunes Artificial Dune •Construct dune seaward of an eroding coastal bank/bluff •Sacrificial •Use coarser sediment for increased longevity Dune nourishment •Add compatible sediment to eroded dunes •Vegetation Vegetation •Use native, salt- tolerant plants with extensive root systems •Establish stable slope •Address invasives Runoff Control •Remove and reduce impervious surfaces •Redirect water •Minimize maintained lawn areas •Use swales and rain gardens Sand Fencing •Thin wood slats & twisted wire preferred •Site landward of annual storm waves •Avoid plastic, metal, fences that become structures Modified Public Access Brewster Coastal Management Needs Analysis •What is the goal? •What are the causes of erosion/damage? –Flooding –Erosion –Waves •Options to address causes? –Upland Runoff? –Vegetative Stabilization? –Reconfigure uses? –Need for stabilization? •Impacts •Benefits •Costs Site-Specific Analysis •Shoreline Change Rate? –Short and long-term •Flood Zone(s): type and elevation(s)? –V zone, A zone •Dry beach width? •Resource type? –Beach, dune, bank, floodplain •Function?