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Options for Managing Coastal Erosion

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Options for Managing Coastal Erosion Options for Managing Coastal Erosion Presentation by: Ashley Sprague Shoreline stabilization methods • Armouring - Boulders/rockwalls most common method of erosion control in Nova Scotia Concerns: - Accelerate erosion - Impact coastal processes - Cut off sediment supply - Access Soft approaches • Fewer people using this approach • Range of native, salt tolerant species Benefits: - Allows coast to function naturally - Habitat, water quality benefits Concerns: - High energy systems Before you build Consider a vegetated setback Living shorelines: An alternative approach Aim to optimize natural functions of the shoreline, while reducing erosion risk Upland area + intertidal zone + shallow water habitat = combined protection benefits Integrated Coastal Management Natural shorelines are dynamic, interconnected and provide many functions Any action has the potential to adversely affect ecosystem services onsite and on larger scale All elements of the shoreline should be considered simultaneously when making a decision How do we decide? Decision tree Different sites require different solutions Factors considered: -Level of bank erosion, bank height -Presence of vegetation, marsh, beach -Wave energy/exposure -Water depth Decision Tree Principles 1) Shorelines should be left in their natural condition unless erosion has the potential to result in significant loss of property 2) Preserve and enhance natural shoreline elements where possible; and 3) Where impacts are unavoidable, locate erosion control treatments where they will have the least overall impact to ecosystem function Fetch Distance across open water over which wind blows and waves are generated Fetch and water depth influence wave height and energy http://ccrm.vims.edu Banks Level of erosion? (low or high) Forested shoreline? Bank height - < 30 feet- Maintain vegetation and prevent large tree falls - > 30 feet - Grade bank and use good upland management practices to prevent further erosion http://ccrm.vims.edu Bank grading - Reduce the steepness of a slope (allow for wave run-up and improve vegetation growing conditions) http://ccrm.vims.edu Before After Presence of a Marsh? Roots and grass stems provide erosion protection Wider marshes = more wave reduction and protection < 15 ft - encourage growth > 15 ft - maintain marsh Can’t force it http://ccrm.vims.edu Marsh Restoration http://ccrm.vims.edu Before After Marsh Expansion A low fetch (< ½ mile) can provide ideal wave conditions for marsh expansion Fill may be needed May require fibre log until roots from the plants are fully established http://ccrm.vims.edu Marsh Sill Higher fetch areas Low-profile stone structure, allows marsh formation /restoration placement depends on bank height, water depth and bottom type http://ccrm.vims.edu Beaches - Nourishment http://ccrm.vims.edu Beaches - Breakwaters An off-shore structure to deflect force of incoming waves and contain sand beach May be needed in actively eroding areas http://ccrm.vims.edu Living Shorelines in Nova Scotia EAC Future project Property assessments with expert team Identify and implement alternative methods Monitor resiliency Overland erosion More high intensity rainfall events Increased area of impervious surfaces High volume and rate of runoff Can lead to erosion issues Stormwater Management Approach to reducing runoff volume, rate and pollutant load Best Management Practices aim to work with natural systems to promote infiltration, evaporation and water capture/reuse ‘Slow it, spread it, sink it” Bioretention area Individual Property Level Reduce impervious surfaces Encourage water infiltration, capture and reuse Opportunities: driveways, rooftops, lawns, plant trees Costco.ca http://bit.ly/yP1aS N Rain barrel Rain garden Neighbourhood Opportunities: parking lots, streets, buildings Vegetated islands Bioswale Take home messages There are options for shoreline stabilization – all will have impacts Allow coast to do the work: - Maintain existing vegetation - Consider options before attempting shoreline hardening Working with neighbours will benefit everyone Blog – www.stormwatercentral.ca Resources Decision Tree Manual: http://ccrm.vims.edu/decisiontree/decisiontree_manual.pdf Contact: Ashley Sprague, Restoration Coordinator Email: [email protected] Phone: 902-442-5046 .
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