Bluff recession along the coastline becomes an ever-increasing concern as high density facilities construction and development in the coastal zone, sustained high water levels, and episodic storm events combine to create severe erosional conditions. Coastal bluff erosion can be caused by two catergories: subaerial and subaqueous processes. Subaerial bluff processes consist of bluff slope stability, bluff face erosion, and bluff toe erosion, occurring at different frequencies and magnitudes. Subaqueous processes include direct wave impact, horizontal retreat of bluff toe materials, and irreversible lakebed downcutting, a common coastal process along cohesive shorelines of the Great Lakes. For the short-term bluff recession, the most successful factor we have established is called Cumulative Wave Impact Height (CWIH) Index, which accounts for water level, wave runup, wind setup, and width of foreshore beach (Brown et al., 2005, Swenson et al. 2006). In the past decade, we have been examining nearshore lakebed downcutting, which is believed to control long-term bluff recession rates in Great Lakes. Studies show that depending on water levels and the thickness of overlying sand, downcutting can occur relatively continuously, compared to bluff recession and affects nearshore bathymetry. As a result waves can further erode intact bluff-toe material, creating a steeper bluff profile, promoting further slope failures, and yielding excessive bluff recession. While we have gained a tremendous amount of understanding the role of lakebed downcutting, obtaining reliable spatial measurements for quantifing spatail variation of bluff recession becomes challenging. Recently we haved succesfully developed the state-of-the-art geophysical method that combines acoustic-wave and electromagentic-wave based technique to effectively measure nearshore sublayer thickness (Lin et al., 2009, 2010). Through successive surveys, the changes of underlying glacial till bottom, i.e. the rate of lakebed lowering (downcutting), can thereby be determined. Ongoing research aims to examine/characterize/predict the evolution of high bluff in front of natural and newly built coastal structures in response to any dynamic subaerial and subaqueous change along Lake Superior and Michigan coastal areas in Wisconsin. The overall goal is to develop a balance between development and conservation with the purpose of optimizing the regional and long-term bluff mitigation strategies.
Shoreline of small lakes plays an important role in overall lake ecosystem. For example shoreline provides habitat and food for a wide variety of flora, fauna, insects and micro-organisms. The interaction with surrounding terrestial and aquatic systems affects the geochemical cycling and aging of these waters. Humans utilize shoreline of small lakes for a variety of recreational activities and enjoy their ecology and beauty. As a result any small change of shoreline in small lakes is critical. Many previous studies have identified that shoreline change of many small inland lakes can be casued by stream/river carried sediment plume, wave induced longshore sediment transport, or ice movement to grind and displace shoreline soil particles. Nevertheless little is known on the shoreline change of a river- lake system (e.g., Yahara river estuary) that can be affected by both seiches-generated reverse flow and wind waves during the open water season and ice-jam erosion during the winter season. Our ongoing research aims to employ a series of SediMeters to monitor the dynamic change of nearshore bottom sediment change caused by current-wave interactions. Successive low-altitude photos will be taken to track shoreline change. Cause and effects of shoreline change will be quantified and incorporated into a coupled hydroydnamic-sediment-shoreline evolution model for small lakes.
Sponsor : Wisconsin
Coastal Management Program
Wisconsin
Alumni Research Foundation
Wisconsin Department of
Natural
Resources
Student Investigators:
Kevin Lin (PhD), Bruce Bessert (PhD)
Erica Hagen (MS), Bill Roznik (MS)
Graduated: Mike Swenson (M.S.), and Lisa Brown (M.S.)
Collabarators:
Professor, David Mickelson, GeoScience, UW-Madison
Professor Dante Fratta, Civil and Environmental Engineering, UW-Madison
Professor Tuncel Edil, Civil and Environmental Engineering, UW-Madison
Opening
Publications:
- Lin, Y.. T, Wu, C.H., Fratta, D., Kung, K.-J.S. Integrated acoustic and electromagnetic wave-based technique to estimate subbottom sediment properties in aquatic environment, Near Surface Geophysics, 8(3), 213-221, 2010.
- Lin, Y.T., Schuettpelz, C., Wu, C.H., and Fratta, D., A., combined acoustic and electromagnetic wave-based technique for bathymetry and subbottom profiling in shallow waters. Journal of Applied Geophysics, 68, 203-219, 2009
- Swenson, M.J., Wu, C.H., Edil, T.B., Mickelson, D.M., Bluff recession rates and wave impact along the Wisconsin coast of Lake Superior, J. of Great Lakes Research, 32(3), 512-530, 2006.
- Brown, E.A., Wu, C.H., Mickelson, D.M., Edil T.B., Factors
controlling
rates of bluff recession at two sites on Lake Michigan, J. of Great
Lakes
Research, 31(3), 306-321, 2005.
- Petykowski, C., Wind wave modeling and verification on small lakes, Master Thesis, Civil and Environmental Engineering, UW-Madison, 2004.
Spatial variation of bluff along the Great Lakes
Combined acoustic & electromagnetic method
Dynamic shoreline change in a river- smal lake system
