Lake Michigan Potential Damages Study

1
Lake Michigan Potential Damages Study

• Preliminary Expectations
• Comments apply to only the five Lake Michigan
  prototype counties
• Allegan Ottawa Counties - Michigan
• Ozaukee, Sheboygan, Manitowoc Counties -
  Wisconsin
• Expected impacts for 50-year planning horizon

2
Hydrologic Scenarios - I

• The five scenarios represent plausible ranges of
  levels for the next 50 years.
• The base case scenario has a similar range,
  mean and extremes to water levels recorded since
  1918.
• The extreme low scenario has a range of 5.7
  feet, with a mean reduced by 1.5 feet from the
  recorded past the extreme low in this scenario
  is 1.75 feet lower than record low (1964).
• The extreme high scenario has a range of 5.6
  feet, with a mean increased by 0.7 feet from the
  recorded past the extreme high in this scenario
  is 1.0 foot higher than record high (1985) flood
  levels approximate the FEMA 500-year open coast
  values in prototype counties.

3
Hydrologic Scenarios - II

• Storm surge / draw-down elevations
  (instantaneous) can range from 1.0 to 3.0 feet
  beyond still water (monthly mean) elevations,
  varying by month disturbed levels in embayments
  (Green Bay, Grand Traverse, Little Traverse) will
  have specialized characteristics that may be
  larger for the open coast.
• Economic impacts are being compiled for only
  three of the five scenarios the base case the
  extreme high scenario and, the extreme low
  scenario.
• The scenarios do not predict when the extreme
  highs and lows will occur within the 50-year
  period only that they will occur sometime within
  this planning horizon.

4
Economic Considerations

• Market values will constantly exceed assessed
  values.
• Affluence is projected to increase under all
  three scenarios.
• Market values for the study period under the
  extreme high scenario for the open coast would
  plateau (at best) and probably fall during high
  water / recession years however, over the entire
  50-year period, market values would be
  significantly higher at the end of the period.
• Market values in rivermouths subjected to
  higher incidences of flooding under the extreme
  high scenario would likely decrease.
• Open coast riparian property values would
  likely soar under extreme low conditions in the
  prototype counties.
• Rivermouth riparian property values under
  extreme low conditions would likely stay constant
  or perhaps decrease slightly.

5
Future Shoreline Development

• Michigan counties would likely see less new
  residential development, but greater affluence
  (mansionization) for the next 50-years regardless
  of lake level scenario.
• Wisconsin counties would likely undergo greater
  land use changes from agricultural to residential
  or commercial/institutional under any of the
  level scenarios and would likely reach full
  development (no vacant land) by the end of the
  study period.
• Under the extreme high scenario with increased
  recession rates, more parcels will be abandoned /
  converted to public holdings and secondary roads
  may be abandoned or relocated.
• Under the extreme low scenario, further
  encroachment into hazard zones will occur for
  open coast and rivermouth riparian properties.

6
Open Coast Structural Protection

• Construction of coastal protection structures
  (revetments, seawalls, groins, etc.) will
  increase by at least 5 per annum under base case
  conditions in all of the Michigan and Wisconsin
  prototype counties.
• A greater demand will likely occur for protection
  structures in both states under the extreme high
  water level scenario this construction would
  further decrease sediment supply locally and
  exacerbate beach erosion and bluff recession
  downdrift.
• Construction of protective structures under the
  extreme low scenario will likely be significantly
  reduced in both states this assumption is
  debatable, particularly in cohesive nearshore
  locations where downcutting becomes severe new
  structural protection would likely also be
  under-designed.
• Under both the extreme high and low lake level
  scenarios, there would likely be an increased
  incidence of damage and destruction of coastal
  protection structures as compared with the base
  case condition.

7
Sediment Budget Impacts - I

• Under the base case condition, increased
  structural protection will likely cause decreases
  in sediment supply, which could be offset over
  the 50-year period by increased supply caused by
  anticipated failures of existing structural
  protection the net change has not yet been
  quantified.
• Under the extreme high scenario, sediment
  supply may have a net increase in the prototype
  counties, due to increased bluff recession and
  failure of most existing private shore
  protection, which is offset somewhat by
  construction of new protective works.
• Under widely varying water level scenarios,
  there may be a decrease in sediment supply caused
  by sand being carried far offshore and
  essentially becoming relict deposits.

8
Sediment Budget Impacts - II

• Under the extreme low scenario, beach widths
  would be larger more often this phenomenon,
  however, would be transient with beach widths
  decreasing whenever lake levels rose, even within
  the newer range.
• Under the extreme low scenario, sediment
  loading from rivermouths will decrease
  substantially, due to shoaling within the river
  channels and dredge disposal on upland areas
  this component, however, is a minor contributor
  to the open coast littoral system.
• Federal navigation structures will continue to
  have an impact on sediment transport throughout
  the five prototype counties under each of the
  water level scenarios being investigated the
  likely impacts of these structures will be
  investigated further.

9
Bluff Recession Rates -Base Case Water Levels

• Lake-side effects on bluff recession rates
  under the base case would be similar in the
  future as in the past water level frequencies
  and extremes would be similar wave energies
  would be similar sediment supply would be
  variable.
• Land-side effects on bluff recession rates
  under the base case over the next 50-years in
  Allegan and Ottawa Counties would likely increase
  due to geotechnical factors (e.g., buildings
  being nearer to the bluff face), surface water
  drainage, deterioration and failure of older
  shore protection and decreased sediment supply.
• Bluff recession rates over the next 50-years in
  the Wisconsin prototype counties will likely not
  undergo as much increase due to less existing
  development, less disruption in sediment supply
  (due to fewer shore protection structures than in
  the Michigan counties), and better hazard
  knowledge.
• Areas with existing structural protection that
  are flanked by unprotected shoreline will have
  similar long-term recession rates as areas
  without protection.

10
Bluff Recession Rates -Extreme High Scenario

• Bluff recession rates will generally remain
  constant over the long-term for most cohesive
  nearshores in the Michigan and Wisconsin
  prototype counties increases may occur for 10
  of the Michigan shorelines and 60 of the
  Wisconsin shorelines in the prototype counties
  further model results will confirm or refute
  these assumptions.
• Current accretion areas will likely lose
  beaches and be exposed to erosion forces not
  previously in place this phenomenon is debatable
  and needs to be confirmed via modeling.
• Further structural protection construction would
  likely cause dramatic increases in erosion of
  poorly protected or unprotected shorelines
  downdrift.
• Areas in both states prone to deep slump
  failures could see increases in recession rates,
  since rising water levels can coincide with heavy
  rainfall events.

11
Bluff Recession Rates -Extreme Low Scenario

• Bluff recession rates would likely decrease
  dramatically for at least 10 of the shorelines
  in Michigan and 60 of the Wisconsin shorelines
  in the prototype counties over the next 50-years
  further model results will confirm or refute
  these assumptions.
• Beach widths would increase dramatically along
  bluff and beach shorelines during low water
  periods.

12
Rivermouth Structural Protection

• Rivermouth structural protection will increase
  in the prototype counties over the next 50-years
  under the base case condition, primarily as a
  function of redevelopment pressures and
  maintenance backlogs.
• Under the extreme high lake level scenario, it
  is expected that there will be pressures for
  extensive rivermouth structural protection
  improvements, maintenance and possible land
  reclamation.
• Rivermouth riparian properties under the
  extreme low scenario will be subjected to
  increased costs for structural rehabilitation /
  improvement and dredging rehabilitation will
  increase due to loss of hydrostatic pressure on
  structures and aerobic decomposition of wood
  structures.

13
Rivermouth Flooding

• Under the base case conditions, there will be
  minor rivermouth flood losses, since most
  riparian properties have been designed or are
  maintained to levels heretofore recorded.
• Under the extreme high scenarios, flooding will
  occur within the FEMA 500-year flood limit
  causing significant losses to the coastal
  communities of Saugatuck / Douglas, Holland and
  Grand Haven / Spring Lake in Michigan and
  Sheboygan and Manitowac in Wisconsin.
• Under the extreme low scenario, no flood losses
  are anticipated in the five prototype counties.
• These studies exclude coincident lake-effect
  flooding occurring at the same time as peak flood
  flows from tributaries.

14
Low Water Impacts - I

• Under the extreme low water scenario,
  significant disruption of recreational boating
  uses will occur in all five prototype counties
  these disruptions may cause permanent changes in
  the commercial and institutional land uses
  associated with boating within the rivermouth
  communities this impact will also be felt under
  the base case conditions, albeit not to the same
  degree or permanence.
• Under the same scenarios, significant losses
  will occur to commercial concerns in the
  rivermouth communities that rely upon
  transportation of goods by water.
• Substantial dredging will be required in each
  of the rivermouth communities to maintain
  existing federal channel depths and approaches to
  private facilities, including manufacturing and
  boating services.

15
Low Water Impacts - II

• Under both the base case and the extreme low
  scenario, significant problems will arise in the
  five prototype counties dealing with disposal of
  dredge materials. Increased quantities of
  dredged material will require upland disposal and
  confinement whenever contaminants are available.
• Increased dredging will decrease water clarity
  and water quality temporarily due to resuspension
  of fine materials and nutrients and changes in
  local circulation patterns.
• Encroachment will increase in the littoral
  zone, particularly for the extreme low scenario.
• Uses of clean sediment for beach nourishment
  could become more prevalent and open water
  disposal issues may likely need to be reopened.

16
Low Water Impacts - III

• Outfalls and intakes within rivermouth
  communities and on the open coast may require
  modification, relocation or abandonment
  particular concern for research needs to be on
  public water supply and wastewater treatment
  facilities supporting coastal communities.
• Groundwater extraction for public and private
  water supply will become more problematic even
  far removed from the Great Lakes coast lines
  rural locations will likely see decreased pumping
  production due to climatologic decreases in
  recharges and decreased exchange between the open
  lake and groundwater aquifers.
• Public knowledge of coastal erosion processes
  will likely suffer physical forces such as
  downcutting will not cease public information
  programs are going to be more critical.

17
Ecological Impacts of Extreme High Scenario - I

• Plants
• Phytoplankton - negligible impacts anticipated
  affected by water clarity primarily
• Periphyton - slight increase anticipated in
  rivermouth areas affected by water clarity
  primarily
• Submerged - possible increases anticipated in
  specific rivermouth areas affected by water
  clarity as well nonindigenous plants may
  increase coverage proportional to increases for
  other species
• Emergent - dramatic decreases anticipated in
  rivermouth areas trade-offs with submerged
  plants.

18
Ecological Impacts of Extreme High Scenario - II

• Invertebrates
• Zooplanton - negligible impact anticipated
  affected by water clarity
• Benthos - shifts will occur depending upon
  plant community changes in rivermouths no
  impacts on open coasts.
• Fish - wetland, riverine and tributary spawners
  and littoral zone fish (bowfin, bullhead,
  steelhead trout, smelt, largemouth bass, yellow
  perch, etc.) would likely all exhibit an increase
  in populations.
• Amphibians, Reptiles, Mammals and Birds - each
  of these groups would likely see an increase in
  populations, depending on preferred habitat.

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Ecological Impacts for Extreme Low Water
Scenario - I

• Plants
• Phytoplankton - negligible impacts anticipated
• Periphyton - slight decline anticipated in
  rivermouth areas
• Submerged - significant decline anticipated in
  rivermouth areas nonindigenous plants may
  increase coverage.
• Emergent - increases anticipated in rivermouth
  areas nonindigenous plants may increase coverage
• Invertebrates
• Zooplanton - negligible impact anticipated
• Benthos - reduction anticipated in rivermouth
  areas no impacts on open coasts.

20
Ecological Impacts for Extreme Low Water Scenario
- II

• Fish - Wetland, riverine and tributary spawners
  and littoral zone fish (bowfin, bullhead,
  steelhead trout, smelt, largemouth bass, yellow
  perch, etc.) would likely all exhibit a marked
  decline in populations.
• Amphibians, Reptiles, Mammals and Birds - each
  of these groups would likely see a marked
  decrease in populations, depending on preferred
  habitat.

21
Lake Regulation ChangesBase Case Conditions

• No major changes are anticipated in Lake
  Superior outflow regulation under the base
  condition.
• Currently, some technical aspects to Plan
  1977-A outflow computations are being explored
  and are likely to be implemented only changes
  the precision of forecasts not the basic
  objectives of the endorsed regulation plan.
• Five-lake regulation schemes will not be
  considered.
• Economic impact assessments could provide
  impetus for a detailed analysis of three-lake
  regulation (Lake Erie) at a later date outside of
  this study.

22
Lake Regulation ChangesExtreme High and Low
Scenarios

• Under both extremes, the performance of the
  Lake Superior outflow regulation plan would
  likely be questioned with some changes possible.
• The economic impacts of extreme water level
  ranges would likely provide impetus for a
  detailed analysis of three-lake regulation (Lake
  Erie) at a later date outside of this study.
• The proponents for detailed three-lake
  regulation analysis of cost - benefits and
  environmental impacts during extreme high
  scenario will likely be mid-lakes riparians and
  coastal communities. The proponents for further
  study during extreme lows would likely be coastal
  communities, recreational boating interests,
  commercial concerns (manufacturing, shipping,
  tourism), and hydropower interests.

23
Land Use Management Options -Base Case Conditions

• Under base case conditions, problem-avoidance
  will continue to prevail.
• Hazard determinations will continue to be
  inconsistent over space and time.
• Newer management provisions (disclosure
  statements, deed restrictions, insurance
  provisos, etc.) would likely find little
  acceptance at local levels.
• Professions that influence shoreline
  development (insurers, banks, zoning and planning
  commissions) would likely have a greater
  influence on coastal siting decisions.
• Over time, more pressures will arise to address
  sand management in the coastal zone in a regional
  context.

24
Land Use Management Options -Extreme High
Scenarios

• Federal programs will likely be pressured for
  emergency short-term aid, while other long-term
  hazard mitigation measures may be advocated
  standardization and more accurate hazard mapping
  will likely be promoted.
• States will likely be pressured to strengthen
  legislation, particularly shoreline management
  options (setbacks, deed restrictions, disclosure
  statements, etc.)
• Under the extreme high and the base case
  scenarios, there will be increasing pressure to
  implement measures to mitigate sand supply losses
  created by the construction of shore protection
  as a condition of permits.
• Local governments will likely be pressured to
  revisit zoning issues.
• Insurance rates will likely increase
  proportional to the risks incurred.

25
Land Use Management Options -Extreme Low Scenario

• Federal programs will likely be pressured for
  emergency short-term aid for dredging and
  emergency rehabilitation or relocation of
  community water systems.
• States will likely be pressured to relax
  regulations dealing with shoreline management
  (e.g., minimum setbacks, variances of local
  zoning) particularly if new beach ridges appear
  to be permanent.
• Enforcement of wetlands protection statutes
  will become more difficult as shoreline owners
  encroach on previously available habitat.
• The role of local governments within the five
  prototype counties for this scenario has not yet
  been fully determined.