Updating Georgia’s Coastal Maps: Collaboration on my Mind
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A discussion of the ongoing Georgia Coastal Mapping Update, a major effort that is progressing by the collaboration of multiple parties. These parties include FEMA, Georgia Department of Natural Resources, contractors and of course, the local stakeholders. Presented by Onur Celik, PE, CFM, of CDM Smith and Todd Harris, PMP, CFM of the Georgia Department of Natural Resources at the Association of State Flood Plain Managers (ASFPM) 2015 Conference.
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Updating Georgia’s Coastal Maps: Collaboration on my Mind
- 1. Updating Georgia’s Coastal Maps Collaboration on my Mind June 2, 2015 Onur Celik, PE, CFM, CDM Smith Todd Harris, PMP, CFM Georgia Department of Natural Resources
- 2. Outline • Project Overview – History – Scope – Collaborating Parties – Outreach • Analyses and Mapping Approach – Coastal Analysis – Riverine Analysis – Mapping/Regulatory Products – Non-Regulatory Products • Conclusion – Q/A
- 3. History – Georgia Flood M.A.P. Program • Increase focus on risk assessment and planning • Continue partnerships with Federal, State, and Local Agencies • Acquire and utilize high accuracy topo data • Deliver risk products and datasets Enhanced Outreach Program • Outreach Guidebooks • Increased Community Engagement • Robust Website (www.georgiadfirm.com) Transitioning State Program to align with FEMA’s Risk MAP Program
- 4. History • Effective Coastal Studies are dated – Current surge analysis is 20 to 40+ years old! Chatham County – ESSA’S JPM Method (1970) Climate data from 1965 to 1981 Glynn and Camden Counties – SURGE model update in 1989 • Riverine Studies are partially up-to date Bryan, Charlton, Effingham, Liberty, Long, Chatham partially updated in 2014 Camden, Glynn, McIntosh analyses were older and did not utilize the current LiDAR data or latest hydraulic models
- 5. History – FEMA Funded Risk MAP projects for 10 Counties in Eastern/Coastal Georgia: • Bryan • Camden • Charlton • Chatham • Effingham • Glynn • Liberty • Long • McIntosh • Newton
- 6. Scope Complete (Inland): – Completed: In Progress (Coastal):
- 7. Collaborating Parties – FEMA contracted AECOM/Baker for Coastal Analyses – Georgia DNR contracted CDM Smith and Dewberry for Riverine Analyses, Production – Inland Riverine Analyses completed and inland counties became effective in 2014 – Coastal Analyses are complete in Spring - Preliminary Maps will be issued tentatively in September
- 8. Outreach Discovery Multi-Agency Coordination Meeting Kick-off (Coastal Update) Meeting H&H-Coastal Modeling Flood Risk Review Meetings Preliminary FIRMs & FIS MARCH 2012 FEB. 2013 FALL 2014 AUG. 2015 SEP. 2015MAY 2014 FALL 2015 PRELIMINARY PROCESSING POST PRELIMINARY PROCESSING FEMA issues Letter of Final Determination Six Month Compliance Period (Ordinance Updates) Resilience Meeting CCO Meeting 90-Day Appeal Period FEMA & GA DNR resolve appeals & protests
- 9. Outreach – Upcoming Flood Study Review Meetings
- 10. Outreach – Property Notification Tool
- 11. Analyses and Mapping Approach • Study Types: – Coastal – VE or AE Zones – LiMWA – Riverine – Detailed/Limited Detailed – Redelineation – Approximate
- 12. Coastal Analyses Determined from storm surge model Components of Coastal Flooding: 1. Storm Surge Stillwater Elevation (SWEL) 2. Wave Setup 3. Wave Height 4. Wave Runup
- 13. Coastal Analyses – Storm Surge • Set up “mesh” for hurricane/surge model • Validated hurricane/surge model • Ran hundreds of hypothetical storms • Resulting storm surge still water elevations for the 1% annual chance event
- 14. Coastal Analyses
- 15. Coastal Analyses – Mapping
- 16. Riverine Analyses 37131.0500 35257.9400 35037.9400 – Types of Analyses – Detailed/Limited Detailed – Redelineation – Approximate
- 17. Riverine Analyses 1200 1400 1600 1800 2000 2200 2400 2600 76 78 80 82 84 Beaverdam Swamp- Approximate Study RS = 54448.14 Station (ft) Elevation(ft) Legend WS 100yr Ground Ineff Bank Sta .12 . 0 6 .12
- 18. Regulatory Products • Upcoming FIRM and FIS Report will follow new Specifications:
- 19. Regulatory Products – FIS Report • Database Driven and more User Friendly Old Format New Format
- 20. Regulatory Products – FIS Report • Map Index in the report for easy reference • Information for 4% (25 Year) Flood (where available):
- 21. Regulatory Products – FIS Report • Future Conditions (if applicable) • Protection Measures:
- 22. Regulatory Products – FIRM • Additional Information (Elevations at 1/10’ increments etc) • New Look, more streamlined legend Old Format New Format
- 23. Regulatory Products – FIRM • User Friendly
- 24. Regulatory Products – FIRM • Additional Information (Elevations at 1/10’ increments etc) • New Look, more streamlined legend Old Format New Format
- 25. Non-Regulatory Product – Changes Since Last FIRM • First Time in Georgia • Provides information to be used for Mitigation/Outreach Activities
- 26. Non-Regulatory Product – Flood Depth Grid • First Time in Georgia • Provides information to be used for Mitigation/Outreach Activities
- 27. Non-Regulatory Product – Wave Height Grid • First Time in Georgia • Provides information to be used for Mitigation/Outreach Activities Example: Wave Height Grid
- 28. Non-Regulatory Product – Risk Assessment Grid • First Time in Georgia • Provides information to be used for Mitigation/Outreach Activities
- 29. Non-Regulatory Product – AOMI • First Time in Georgia • Provides information to be used for Mitigation/Outreach Activities
- 31. Questions/Comments??? Todd Harris, GADNR, Todd.Harris@dnr.ga.gov Onur Celik, CDM Smith, Celiko@cdmsmith.com
Editor's Notes
- Thanks again for being here. In this session, we will discuss the ongoing Georgia Coastal Mapping Update, a major effort that is progressing by the collaboration of multiple parties. These parties include FEMA, Georgia Department of Natural Resources, contractors and of course, the local stakeholders. For this project, Georgia DNR has undertaken riverine analyses, mapping and outreach activities. DNR’s project manager Todd Harris and myself would like to discuss about this work, and the upcoming products including Georgia’s first non-regulatory products.
- First, Todd will provide us the history of Georgia’s map update efforts. He will then give us specifics of this particular project with an emphasis to the outreach activities. Later, I would like to present further details of different study types, and the upcoming products. Finally, we will conclude with the tentative map release schedule and answer questions you may have.
- As Todd described, the analyses were separately performed for coastal and riverine areas. The coastal analyses result in determination of coastal VE and AE zones and the maps will present a new feature called LiMWA. We will discuss about this feature in details shortly. The riverine analyses were performed in detailed/limited detailed, redelineation and approximate methods which all used the latest LiDAR data. The detailed and limited detailed analyses also utilized survey data. Let’s take a look at them in further detail:
- Here is a Visual for coastal analyses components that were taken into consideration: Stillwater Elevation Before a hurricane makes landfall, the combined effect of circulating winds and drop in air pressure causes a rise in sea level. When it reaches the shoreline, the seafloor forces this rise to increase dramatically. This is called Stillwater Elevation. It is the largest component of coastal flooding. Wave Setup As waves batter (hit) the coastline for several hours, they tend to “pump” up the water surface higher than the stillwater elevation. This effect is referred to as wave setup. Wave Crest Elevation ride atop the storm surge plus setup Wave Runup When waves hit the shoreline, its momentum forces it upward particularly where there are bluffs, dunes, or man-made structures. The additional height is called wave runup.
- In order to estimate the stillwater elevations, the coastal team used a very dense mesh of topographic data, investigated the historic events and ran hundreds of hypothetical storms to estimate the magnitude of a storm causing the 1% annual chance event. They then modeled areas that are subject to wave action and runup.
- As a result, the coastal floodplain boundaries were determined. The areas determined to have high wave action are V (velocity) Zones. These areas will be subject to waves of 3 feet or higher. The areas being impacted by coastal flooding but with wave heights of less than 3 feet are Coastal A zones. Although these Zones have lower waves they may still be subject to moderate wave action. So, planning purposes the maps will show the limit for the moderate wave action which is defined as waves between 1.5 to 3 feet. This line is called LiMWA – Limit of Moderate Wave Action.
- Here is an example of typical coastal mapping with a LiMWA line depicting the landward limit of areas subject to moderate wave action.
- After this quick glance to the coastal analyses, let’s talk a little bit about the riverine. All analyses are model backed and utilizing the LiDAR Information. Detailed/limited detailed reaches also included survey data. The visual may provide a perspective to the typical riverine modeling. We use models that calculate flood elevations at the cross-sections based on estimated discharges.
- The cross-sections include the topographical information of the river channel and the overbank areas.
- We so far covered the background of the project and study types. Now let’s focus on the products. For this project and all later iterations FEMA’s latest standards are followed. These standards bring significant improvements. Georgia is one of the first states getting these products.
- Along with the regulatory FIRM and the FIS report, the communities will receive non-regulatory products. This slide shows an example of Changes since Last FIRM product. It is a visualization of changes to the proposed floodplain extents since the last FIRM.
- Additional grids allow for visualization of estimated flood characteristics such as flood depth, water surface elevation, multiple frequencies and velocity.
- Wave Height grids depicted wave heights in 3 different categories: > 3 ft, 1.5-3 ft and less than 1.5 ft. This was selected due to the LiMWA guidance that was implemented on all coastal studies. Depth of 1.5-3 ft represented LiMWA areas where coastal construction can be regulated differently.
- This dataset presents potential economic losses based on flood exposure of building stock including critical infrastructure.
- Areas of Mitigation Interest (AoMI) This dataset is an insight into existing or future risk mitigation needs or critical structures.
- To sum up, We discussed the scope of this project, collaborating parties and products that will become available. The next step is a flood risk review meeting. At that meeting, the communities will see the workmap products for the first time. Then tentatively on September 30, the communities will receive the preliminary products. Another meeting will follow (CCO Meeting) which will initiate the appeal/comment period. And once all data is finalized the non-regulatory data will also be relesed. So long story short, the products are soon becoming available for your use. Unless Todd wants to add something, This concludes our agenda.