Czm great marsh_20131114sm

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Sea Level Rise: Natural Resource Impacts and Considerations for Great Marsh Community Resilience

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Czm great marsh_20131114sm

  1. 1. Sea  Level  Rise:  Natural  Resource   Impacts  and  Considera8ons  for   Great  Marsh  Community  Resilience   Julia  Knisel,  Coastal  Shoreline  and  Floodplain  Manager   Kathryn  Glenn,  North  Shore  Regional  Coordinator   Massachuse8s  Office  of  Coastal  Zone  Management  
  2. 2. Coastal  Inunda8on  Mapping  Elements   •  Water  Level:   –  Local  @de  ranges   –  Sea  level  rise  data  &  projec@ons   –  Flood  event  data  (surge  &  precipita@on)   •  High  Resolu8on  Eleva8on  Data:   –  Topographic  &  bathymetric  LIDAR   –  Digital  eleva@on  models  referenced  to   @dal  datums     •  Natural  &  Human  Responses:   –  Current  ecosystems  (beaches  &   wetlands)   –  Landform  changes  (erosion  &  accre@on)   –  Physical  barriers  to  migra@on   (development,  seawalls,  culverts,  etc.)  
  3. 3. Cri8cal  Parameters  for  Modeling  Marsh  Migra8on   Marshes  on  the  Move,  2011   •  If  sediment  accretes  (traps  on  surface  or  accumulates)  as  fast  as   sea  level  rises,  then  marsh  may  avoid  being  converted  or   submerged  
  4. 4. Mean  Higher  High  Water  Tidal  Datum  
  5. 5. Sea  Level  Rise  Scenarios  
  6. 6. Historic  Rate  of  Sea  Level  Rise   (Boston  Tide  Gauge)   •  Mean  range  (MHW-­‐MLW)  =  9.5  feet   •  Record  =  1921-­‐2012  (91+  years)   •  Sea  level  rise  =  0.9  feet/100  years  
  7. 7. Historic  Sea  Level  Trends   from  1921  to  2006-­‐2012  (Boston)   •   Linear  mean  sea  level  rates  (        )  &  95%  confidence   intervals  (mm/yr)  calculated  from  1921  to  recent  years   (2006-­‐2012)  at  the  NOAA  Boston  @de  gauge  sta@on   •  Values  are  trend  of  en@re  data  period  up  to  that  year  
  8. 8. Great  Marsh  Sediment  Accre8on   •  •  Marshes  accrete  by  trapping  sediment  &  by  organic  ma8er   accumula@on  from  roots  &  rhizomes   Maximum  accre@on  for  Great  Marsh  currently  recorded  ~  6  mm/yr   Courtesy  of  Anne  Giblin,  Marine  Biological  Lab  
  9. 9. Wetland  Types   Eleva@on   66%  wetland   Majority   Mean  High   Water  Spring   Mean  High   Water   Mean  Tide   Level   Mean  Low   Water   Water   Unconsolidated   Salt   Shore*   Marsh   Brackish/     Freshwater   Transi@onal   Wetlands   Dry  Lands   *includes  silt,  sand,  or  gravel  that  is  subject  to  inunda@on  and  redistribu@on  due  to  the  ac@on   of  water;  substrates  lack  vegeta@on  
  10. 10. Marsh  Migra8on  Limited  by   Development  &  Infrastructure  (Newbury)   Current   75-­‐Year  Time  Horizon  (2080)     Net  marsh  impact  =  MHHW  +   4.5  l  sea  level  rise  –  1  l  accre@on  
  11. 11. Marsh  Migra8on  Limited  by   Development  &  Infrastructure  (Salisbury)   Current   75-­‐Year  Time  Horizon  (2080)     Net  marsh  impact  =  MHHW  +   4.5  l  sea  level  rise  –  1  l  accre@on  
  12. 12. Marsh  Conversion  to  Unconsolidated  Shore   (Gloucester)   Current   75-­‐Year  Time  Horizon  (2080)     Net  marsh  impact  =  MHHW  +   4.5  l  sea  level  rise  –  1  l  accre@on  
  13. 13. Marsh  Conversion  to  Unconsolidated  Shore   (Salisbury)   Current   75-­‐Year  Time  Horizon  (2080)     Net  marsh  impact  =  MHHW  +   4.5  l  sea  level  rise  –  1  l  accre@on  
  14. 14. Marsh  Migra8on  Modeling  Resource   www.csc.noaa.gov/digitalcoast/publica@ons/marshesonthemove  
  15. 15. Applying  SLR  Data/Mapping   •  Great  Marsh   communi@es  are   currently   grappling  with   retrofinng  areas   that  were   developed   before  SLR  and   climate  change   issues  were   recognized  
  16. 16. Applying  SLR  Data/Mapping   •  Past   experience   •  What  do  we   know  now?   •  What  can  we   do   differently?   •  What  have   we  learned?  
  17. 17. Altera8ons  that  Limit  Natural  Resilience   •  Development  in  flood   prone  areas   •  Impervious  floodplains   •  Culverted  streams  and   rivers   •  Tidal  restric@ons   •  Armored  river  and  coastal   banks   •  Hardened  shorelines   •  Barriers  to  marsh   migra@on   NOAA  photo  
  18. 18. Altera8ons  that  Limit  Natural  Resilience   •  Development  in  flood   prone  areas  
  19. 19. Altera8ons  that  Limit  Natural  Resilience   •  Impervious   floodplains  
  20. 20. Altera8ons  that  Limit  Natural  Resilience   •  Confined   stream  and   river  beds  
  21. 21. Altera8ons  that  Limit  Natural  Resilience   •  Tidal  Restric@ons   •  Causeways   •  Low-­‐lying  roadways  
  22. 22. Altera8ons  that  Limit  Natural  Resilience   •  Armored  river  and   coastal  banks  
  23. 23. Altera8ons  that  Limit  Natural  Resilience   •  Hardened  shorelines  
  24. 24. Altera8ons  that  Limit  Natural  Resilience   •  Barriers  to  marsh   migra@on   Photo:  Maine  Sea  Grant  
  25. 25. Altera8ons  that  Limit  Natural  Resilience   •  Dams   •  Culverts  
  26. 26. Sea  Level  Rising/Climate  Changing:     Key  Resource  Func8ons  to  Consider   •  A8enua@on  of      flood  waters   •  Ability  of  storm/flood   waters  to  recede   •  Sediment  availability   and  transport   •  Energy  dissipa@on   •  Natural  resource   adapta@on   •  Ecosystem  con@nuity  
  27. 27. AXenua8on  of  Flood  Waters   •  Limit  impervious  areas   •  Preserve  open  space  in   developments   •  Incorporate  LID   •  Avoid  hardening   stream  and  riverbanks   •  Rethink  new   development  in  flood   prone  areas  
  28. 28. Ability  of  Storm/Floodwaters  to  Recede   •  Limit  new  impervious/ incorporate  LID  and   •  Address  restric@ons  and   inappropriate  culvert   designs   •  Dam  removal   •  Preserve  open  space  in   developments   •  Where  do  floodwaters   go?   •  Consider  ousall   loca@ons   AP  photo   Reuters  photo  
  29. 29. Sediment  Availability  and  Transport   •  Unarmored  banks   •  Bioengineering   alterna@ves   •  Re-­‐nourishment   •  Open  pilings  for   development   •  Re-­‐vegeta@on  
  30. 30. Energy  Dissipa8on   •  Protect  dune  stability   •  Sediment  supply   •  Maintain  floodplain   func@on   •  Sol  bank  stabiliza@on   techniques  
  31. 31. Natural  Resource  Adapta8on   •  Marsh  migra@on  and   accre@on   •  Barrier  beach  migra@on    
  32. 32. Ques8ons?   Julia  Knisel   CZM  Coastal  Shoreline  and  Floodplain  Manager   617-­‐626-­‐1191;  julia.knisel@state.ma.us   Kathryn  Glenn   CZM  North  Shore  Regional  Coordinator   978-­‐281-­‐3868;  kathryn.glenn@state.ma.us  

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