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