The source of sand for perched dunes is the high bluff along their lakeward edge. Grand Sable Dunes on Lake Superior and Sleeping Bear Dunes on Lake Michigan are featured attractions of national lakeshores under National Park Service management. Nourishment of perched sand dunes and the issue of erosion control in the Great LakesĪlthough limited in coverage, perched sand dunes situated on high coastal bluffs are considered the most prized of Great Lakes dunes.

Rates of bluff retreat derived using DSAS vary from unresolvable to as much as 2.2 m/yr, averaging

Maps were analyzed at a scale of 1:120 in ArcGIS and the bluff crest was identified primarily by the visual-break-in-slope method. DEMs, hillshades, and slope and contour maps were generated from bare-earth 19 LiDAR data, and checked against 2005 aerial ortho-photography. Bluff slopes range from 20-90 degrees, beaches are narrow (wide) or absent, and the bluffs are seasonally shielded by ground-freeze and lake ice. Bluffs along the 20 km coastal study site consist of up to 26 m of unlithified Quaternary sediments overlying a 1-4 m ledge of sub-horizontal Devonian shale and sandstone. Short-term recession data can be more useful, cost-effective, and accurate than long-term analyses that use lower-resolution field measurements, T-sheets, and historical aerial photography. High resolution LiDAR data covering a one-decade time frame (1998-2007) permit bluff-crest mapping on two comparable data sets that captures change within a timeframe similar to CZM planning intervals.

The goal of this study is to evaluate spatial variability in bluff retreat rates along a 20 km sector of Pennsylvania's short Great Lakes coast. Land loss is of concern to environmental agencies because land-use planning should account for spatial and temporal variability in land-loss rates, and because bluff erosion contributes to a temporary degradation in coastal water quality. These Quaternary strata are subject to subaerial and lacustrine erosional processes that cause permanent coastal land loss at spatially variable rates, with the former (runoff, slumping, groundwater focusing, etc) dominating over the latter (wave and current scour, abrasion, etc). On the Great Lakes coast of Pennsylvania, Quaternary clay-rich glacial till, paleo- lake plain, and sandy strandplain sequences overlie Devonian bedrock. Short-Term Bluff Recession Behavior Along Pennsylvania's Great Lakes Coastline, USAĬoastal bluff retreat is a common problem along the world's unconsolidated coastlines.

The bluff by emma st clair