Presentation on theme: "Oct. 1998 July 2009 2001 2008 Monitoring Shoreline Change Geological Survey of Canada, Atlantic (GSCA) Bob Taylor, Dartmouth NS."— Presentation transcript:
Oct. 1998 July 2009 2001 2008 Monitoring Shoreline Change Geological Survey of Canada, Atlantic (GSCA) Bob Taylor, Dartmouth NS
Historical framework.........for examining shoreline change in the Gulf of St Lawrence Geogr. Branch. 1959, Gosselin, 1972, LRIS, 1988
Shoreline sites Monitored by GSCA Time frame: Shore measurements 1980-2006 Aerial video surveys: 1984-2000 (10 sites ) (12 sites) (5 sites ) 302 sites Atlantic Canada 27 sites in Southern Gulf
Objectives: repetitive survey and photographic measurements at representative shore sites Define natural phases and duration of shoreline change, ie. erosion, stability and accretion. Document impact of storms and shoreline resilience to these events. (flooding, landward migration). Document human activities and impacts on shoreline stability. Develop a baseline / index of “typical” types and rates of shoreline change..........for future comparison. http://gsc.nrcan.gc.ca/coast/index_e.php
Top Cliff Retreat 1981-2009: glacial deposits only vs on rock LocationNo. of Years Mean Loss (m) Max. Loss (m) Retreat Rate (m/yr) Pleasant Bay 126.96.36.199 Caribou285.07.10.19 Broad Cove 188.8.131.52 Cape John 184.108.40.206 Geogr. Branch: (1930s-1960) 0.18 to 0.4m/yr Gosselin: (1930s-1970) 0.15 to 0.6m/yr
2009 1983 Long -Term Beach Recovery from commercial sediment extraction Belfry Beach, Cape Breton Island
Field Measurements vs Remote Sensing ocean Shore cliff 1945 - 2003 New technology – larger areas covered but may not include local area suitable for rock shores provides a rate of net change over set time intervals Misses interim period and timing of changes Similar mean rates of retreat 0.4 m/yr yet variable over time –max rate?
1.People often perceive shoreline erosion as much greater than it is in reality (long term) - result of negative media and people see the worst in crisis situations -demand remedial action immediately. - shorelines can respond and repair themselves naturally. 2. Decisions about shoreline repairs are often made at time of crisis, no time for consultation of monitoring results. -plans should be made earlier in a proactive mode. Thoughts for Discussion 3. News is short (days to months +anniv), Memory is longer (10-15 yrs); and Interest is cyclic (25-30 yrs).
2. There is no one agency monitoring and archiving long term shoreline changes (physical) and no long term baseline references to evaluate magnitude of shoreline responses. 1. In past - Field monitoring lasted months to ~ 3 years, (university or community) continuity often broken and information not archived nor easily accessible in time. More Thoughts for Discussion Photo C. Currie
4. GIS and GPS technology and satellite remote sensing will be the way of the future but need to maintain the "feel" and understanding of why shoreline changes are occurring. -Shediac and Clyde River examples Even More........... 3. No one agency assessing the impacts of shore protection structures which would improve future decisions and advice. -Different attitudes to shore protection structures evolve with time, eg, groynes. -scale of human activity at coast unanticipated. Photo EAC
Community Strength - local knowledge & drive. Document local conditions pertinent to their geographic area 2. Log date of storm events –flood levels and extent from rivers, waves or storm sewers. 3. Photo, mark and log:- wave run-up limits, dune and cliff retreat, washover channels cut into dunes, opening and closing of tidal channels. 4. Repetitive photos from established locations -at set interval and after storms (need same person / camera specs used). 1.Establish key locations (and maintain shoreline markers) for repetitive surveys.
Community Strength – proximity & concern. 5. Note significant changes in vegetation limits, sediment levels at structures or human infrastructure in shore zone. 6.Alert provincial/ federal agencies about physical changes and need to resurvey. Lobby for support and results.