options for managing coastal erosion - ecology action · coastal erosion presentation by: ashley...
TRANSCRIPT
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
Before After
- Reduce the steepness of a slope (allow for wave run-up and improve vegetation growing conditions)
http://ccrm.vims.edu
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 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 - 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/yP1aSN
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