The influence of changes in water levels as a result of alternate hydrologic scenarios or modifications to the regulation procedures must be assessed in term of alternate costs of structural protection. Baird and Associates developed preliminary estimates of avoided costs for structural protection as part of the 1992 International Joint Commission (IJC) Levels Reference Study.
In the LMPDS, the following subtasks were performed:
1) Assess the response of riparians to both an increase and a decrease in the frequency and magnitude of high lake levels (i.e. there may be more or less pressure for implementation of shore protection) and assess the effectiveness of likely riparian responses and the consequences thereof
2) Assess the costs of higher or lower design crest elevations on the per meter cost to implement shore protection;
3) Estimate of Future Costs For Shore Protection
The influence of changes to future water levels as a result of alternate hydrologic scenarios or modifications to the regulation procedures must be assessed in terms of alternate or avoided costs of structural protection.
To do this, two key tasks were carried out. First, the LMPDS Study Team retained the Planning and Zoning Center to conduct a series of Focus Group sessions with riparian interest groups. The purpose of the focus groups was to assess the response of riparians to both an increase and a decrease in the frequency and magnitude of high lake levels (i.e. there may be more or less pressure for implementation of shore protection). Focus group findings will be used to help assess the costs of higher or lower design crest elevations on the per meter cost to implement shore protection; and, assess the effectiveness of likely riparian responses and the consequences thereof (some shore protection will reduce damages, while other types of shore protection may not reduce damages at all or even aggravate damages downdrift; hence, a decrease in erosion losses may not result from an increase in structural protection).
Focus Group Methodology
Two focus groups were held, one each in Wisconsin and Michigan. The Michigan focus group was held at the Howard Miller Community Center in Zeeland, which is in Ottawa County, only about 6 miles from Lake Michigan. The Wisconsin focus group was held at Lakeshore Technical College, in the village of Cleveland, about 10 miles north of Sheboygan, in Manitowac County. The village is in Cleveland Township, a shoreline community. In addition, a test of the focus group model was held in Lansing, Michigan, with Lake Michigan property owners invited who had primary residences in Lansing. Fourteen persons participated in the Michigan focus group, fourteen in Wisconsin and five in the test session.
Following introductions, there was a discussion of the purpose of the focus group and how it would be conducted. Participants then watched a short, projected, MSPowerpoint slide presentation about how and why Lake Michigan levels change and the historic extent of that change, the effects of that change and a prediction of potential change scenarios over the next 50 years. The major content of the discussion was prompted by a series of questions. Participants brainstormed answers to the questions. Brainstorming comments were written on a flip chart so all participants could see what was recorded. In addition, the sessions were video-taped so that the consultant team could verify comments when analyzing the results.
Following the discussion session, participants were asked to fill out a five-page survey that addressed the physical conditions of their property (if they owned shoreline property), and questions about how rapidly they would respond to a hazard and at what level of damage and investment they would respond. The survey also asked what types of actions they would take, such as constructing shore protection, lobbying for governmental action, selling their property or others. The survey asked for a response about their own properties and about how they believed other property owners might act. Twenty-six surveys were returned.
Focus Group Findings
Detailed comments and observations of the individuals attending the Focus Group sessions can be obtained through the full report entitled, "Prediction of Responses to Hazards Related to Lake Level Change" which can be downloaded from the LMPDS Document Clearing House. Presented here is a summary of the various points of apparent agreement that were gleaned from the dozens of comments by focus group participants.
The motivation to be at the waters edge and to invest in it is high for all who can afford it. This motivation remains high even when faced with the risks of property damage and financial loss.
Among shoreline property owners and local officials, the belief is that there is no clear, coordinated governmental effort to respond to development risks in the hazard zones.
The appropriate governmental roles (as expressed following a specific question to that effect) are:
- Federal
- Identify a practical solution for damage reduction
- Implement the solution if possible
- Educate property owners and local officials.
- State
- Act consistently when dealing with property owners
- Back up local governments with adopted regulations with teeth, but dont impose unfunded mandates
- Education of property owners and local officials
- Local
- Zoning implementation, but deferral to state agencies will be common because locals dont want to be the "bad guy."
- Encourage appropriate development.
The majority of shoreline property owners are willing to invest in protective measures at least once.
The majority of shoreline property owners believed some form of rip-rap of bluffs to be the approach most likely to work and to be approved in areas where bluff erosion takes place.
The majority of local officials believe deep setbacks of residential or commercial structures is the most appropriate response to erosion hazards. Only a few were aware of the option of moving structures back from the bluff.
Recognition of the link between high water levels and bluff erosion is strong among participants but the understanding of shore processes and the relationship of shore process to protection methods is low.
Participants believe that there are land use planning and zoning tools that could help limit structural damages if applied, but that they are rarely utilized effectively.
In the shoreline setting, property rights are important but of necessity tempered slightly compared to non-hazard areas.
There is a widespread awareness -- but very limited understanding -- that Lake Michigan and the estuaries are tied to valuable ecosystem resources, such as wetlands.
The objective of this task is to assess the costs of requiring higher and lower design crest elevations for shore protection structures on a per meter cost basis. More specifically, design crest elevations will be varied above and below a baseline structure height to assess the impacts on cost.
The discussion below describes and summarizes the results for the assessment of cost impacts due to an increase or decrease in design crest elevations for three typical structures. Specifically, the following structures were identified and will be evaluated to assess potential cost impacts for higher and lower design crest elevations:
1. Seawall/bulkhead - Steel Sheetpiling
2. Revetment - Riprap Revetment
3. Groins - Concrete grout-filled geotextile groins
The shore protection structures evaluated are based on designs developed using standard coastal engineering procedures. The results from this report are specific to Lake Michigan, but the methodology used may be used to assess cost impacts associated with changes in crest height on other shorelines.
Design Considerations
To assist in the evaluation, design criteria for each shore protection type along with general assumptions and typical design considerations were established. Depending on the local, state, and federal regulations, different requirements may exist for implementing shore protection. A shore protection structure may be designed and installed to varying standards - such as by a professional engineer, marine contractor, or individual property owner. For this evaluation, it is assumed that shore protection structures will be designed by a professional engineer and installed by a qualified marine contractor. Therefore, the design guidelines set by the Corps of Engineers as indicated in engineering manuals such as the Shore Protection Manual (SPM), Design of Coastal Revetments, Seawalls, and Bulkheads (EM 1110-2-1617), and Coastal Groins and Nearshore Breakwaters (EM 1110-2-1614) will be utilized in this evaluation.
Water Level Impacts on Design Criteria
The overall impact of changing water levels on design criteria should be considered with regards to maximum design water levels. The maximum design water level dictates the height of the structure. It is needed to estimate the maximum wave height at the structure, the amount of runup to be expected, and ultimately the required design crest elevation of the structure. Design still water lake elevations are typically obtained from historical observations of gauging records nearest to the project site.
Under scenarios of increasing water levels, it is assumed that design water levels typically used, such as the 20-year return period still water elevation, would be increased in response to higher recorded lake levels.
Under design scenarios of decreasing water levels, it is reasonable to assume that 20-year design water level elevations would be reduced.
Low water levels may increase the scour potential at the site due to wave action occurring at the base of the structure. This may require widening toe protection lakeward to prevent undermining of the structure.
Costs
The first step in assessing the relative changes in cost due to changes in design water levels was to develop a basic or reference design using existing design standards for the typical shore protection structures. Structures for residential shore protection based on typical conditions for Lake Michigan were selected as the "existing" structures. Once the existing structure design and cost procedure were established, changes in design crest elevations were made and the resulting costs for implementation tabulated. Since the focus of this evaluation was on the relative changes to implement new shore protection, modifications or repairs of existing shore protection are not evaluated.
The basic costs of shore protection include design costs, permit fees, materials, mobilization and demobilization of construction equipment, construction labor, and operation and maintenance. It is assumed that operation and maintenance costs will not vary significantly with relatively small changes in structure elevations. Therefore, operation and maintenance costs are not considered. The costs of the remaining elements are assumed to remain constant regardless of lake level except for construction labor and materials.
The construction labor and material elements that are most likely to change due to the change in lake level are included in the evaluation of the structures cost. The remaining elements, including site preparation costs for site clearing, excavation (except in terms of toe protection), grading, splash aprons and drainage systems on landside were assumed to be equal for each structure and were not included in the total cost of each structure.
Cost estimates for the various construction elements were obtained from the Means 1999 - Site and Landscaping Cost Book as well as from conversations with local quarries in Michigan. Cost estimates are presented as base national averages, but can be converted to costs at various locations around Lake Michigan.
Results
Various shore protection structures and methods have been implemented along the Lake Michigan shoreline. Characteristics such as beach slope, soil conditions, water depth, and wave height, which dictate the design of a shore protection structure, vary from site to site. A general, as opposed to a site-specific approach was taken to assess potential cost changes. A site-specific study would require an enormous effort in data collection, calculation and compilation. Thus, our evaluation was based on two typical Lake Michigan shore protection structures. Utilizing the typical shore protection structures implemented along the Lake Michigan shoreline, the typical cost increase or decrease corresponding with a change in crest height could be determined.
The results of this evaluation provide the costs and percent increases or decreases in cost for the implementation of typical shore protection structures on Lake Michigan. The table (click on table for full size version) below presents a summary of the cost per meter for the riprap revetment and steel sheetpiling for 1 ft, 2 ft, and 3 ft above and below an "existing" design crest elevation of 5 ft. A design crest elevation of 5 ft is utilized because this height was identified as the typical height of shore protection structures in the study area. It should be noted that results from this evaluation should not be used for design or evaluation purposes for a specific site. In designing a specific structure for a site, it is recommended that site-specific information be obtained.
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