Coastal Flood Risk Study Project for Northeast Florida Study Area

Transcription

1 Coastal Flood Risk Study Project for Northeast Florida Study Area Duval County, Florida Flood Risk Review Meeting September 22, 2015

2 Introductions Risk MAP Project Team FEMA Region IV BakerAECOM, FEMA Mapping Partner Project Stakeholders Community CEOs Community FPAs Political Representatives Other State and Federal Agencies Public 2

3 Why We Are Here Project Review and Update Data Collected Modeling Approaches Hurricane Surge Overland Waves Questions and Answers Open Discussion of Draft Work Maps Nassau County, FL 3

4 FEMA Coastal Flood Risk Study Is Not Evacuation Study 4

5 Project Area NEFL Florida Coastal Counties Bryan Duval Camden Flagler Chatham Nassau Glynn St. Johns Liberty Volusia McIntosh 5

6 Why the Coastal Flood Risk Study Is Being Updated Flood risk changes over time Effective study based on outdated hurricane modeling and topographic data Ability to more accurately define risk and account for significant development in project area To gain a complete and current picture of coastal flood risks. This helps community: Plan for the risk Communicate the risk to your citizens Take action to reduce flood risk to lives and property Build smarter and safer 6

7 Why the Coastal Flood Risk Study Is Being Updated (Cont d) Current surge analysis is 30 to 40+ years old SURGE FEMA Coastal Flood Storm Surge Model, last updated1988 Climate data from 1975, 1978, and 1979 NOAA reports Your risk is better defined through Updated elevation data (topographic data and aerial imagery) New climatological data based on recent storms Computing resources a lot has changed in 30 years! Updated coastal hazard methodologies/modeling Improvement in Geographic Information System (GIS) technologies to improve coastal mapping accuracy 7

8 Outreach Meetings Kickoff Meetings November 2010 Technical Update Meetings April 2013 Storm Surge Analysis Update Meeting April 2014 Flood Risk Review Meeting Today 8

9 Basic Elements of a Coastal Flood Risk Study Base Flood Elevation (BFE) on FIRM includes four components: 1. Storm surge stillwater elevation (SWEL) Determined from 2. Amount of wave setup storm surge model 3. Wave height above storm surge (SWEL) elevation 4. Wave runup above storm surge elevation (where present) 9

10 Gathered Field Data Coordinated with community officials and stakeholders regarding available data Conducted thorough data investigation Conducted field investigations for surge and overland wave modeling efforts 10

11 Gathered LIDAR, Topographic Data LIDAR systemgenerated data Gathered bathymetric data 11

12 Gathered Bathymetric Data 12

13 Seamless Digital Elevation Model 13

14 Hurricane Model Mesh Development 14

15 Hurricane Model Mesh Development (Cont d) 15

16 Hurricane Model Mesh Duval County Jacksonville, FL 16

17 Hurricane Model Mesh Duval County (Cont d) Jacksonville, FL 17

18 Hurricane Model Mesh Development 18

19 Comparison of Old Mesh Versus New Mesh 19

20 Hurricane Modeling Validate Tidal Elevation Modeling Review historical storms Pick five storms to validate the hurricane/surge model Generate hundreds of hypothetical storms 20

21 Validation Storm Selection: Tidal Elevations 21

22 Storm Climatology: In Study Area Tropical Storms: Passing within 175 nm of Jacksonville Limited data before

23 Validation Storm Selection: Significant Surge Events Criteria Sorting of Storms 1. Local Landfall 2. Significant WL Difference 3. WL Data Availability (> 3 Stations) 4. Wave Data Availability (2 or more stations) Cleo Dora David Chris Edouard Tammy Fay Dora (5.91 ft) David (5.55 ft) Jeanne (4.22 ft) Tammy (4.07 ft) Fay (3.99 ft) Frances (3.85 ft) Gabrielle (3.82 ft) Floyd (3.8 ft) Ophelia (3.04 ft) Abby (2.93 ft) Irene (2.92 ft) Bertha (2.62 ft) Bob (2.44 ft) Erin (2.43 ft) Cleo (2.35 ft) Dennis 99 (2.24 ft) Frances (15) Charley (14) Jeanne (14) Ophelia (9) Tammy (9) Dennis 99 (8) Edouard (8) Floyd (7) Irene (7) Fay (6) David (5) Frances (5) Ophelia (5) Tammy (5) Fay (5) Jeanne (4) Edouard (3) Charley (3) Chris (2) Dennis99 (2) Floyd (2) Irene (2) 23

24 Validation Storm Selection: Significant Surge Events (Cont d) Criteria Sorting of Storms 1. Local Landfall 2. Significant WL Difference 3. WL Data Availability (> 3 Stations) 4. Wave Data Availability (2 or more stations) Cleo Dora David Chris Edouard Tammy Fay Dora (5.91 ft) David (5.55 ft) Jeanne (4.22 ft) Tammy (4.07 ft) Fay (3.99 ft) Frances (3.85 ft) Gabrielle (3.82 ft) Floyd (3.8 ft) Ophelia (3.04 ft) Abby (2.93 ft) Irene (2.92 ft) Bertha (2.62 ft) Bob (2.44 ft) Erin (2.43 ft) Cleo (2.35 ft) Dennis 99 (2.24 ft) Frances (15) Charley (14) Jeanne (14) Ophelia (9) Tammy (9) Dennis 99 (8) Edouard (8) Floyd (7) Irene (7) Fay (6) David (5) Frances (5) Ophelia (5) Tammy (5) Fay (5) Jeanne (4) Edouard (3) Charley (3) Chris (2) Dennis99 (2) Floyd (2) Irene (2) 24

25 Validation Storm Selection: Significant Surge Events (Cont d) Five validation storms selected Hurricane Dora (1964) Hurricane David (1979) Hurricane Frances (2004) Tropical Storm Tammy (2005) Tropical Storm Fay (2008) 25

26 Validation Storm Selection: Significant Surge Events (Cont d) 26

27 Validation Storm Selection: Significant Surge Events (Cont d) 27

28 Validation: Summary Validation completed for tides and five historical storms Demonstrated model capability to reproduce water levels and waves in project area Comparisons to available data showed reasonable agreement for water levels and waves 28

29 Hypothetical Storms Develop using 5 parameters Central pressure Radius to maximum winds forward speed storm heading Holland s B (shape parameter) Simulate whole range of possible storms for FL (based on historic data for area) Run storms on high-speed computer Quality control results 29

30 Hypothetical Storms (Cont'd) 30

31 Surge Modeling Gives 1% ACE Set up mesh for hurricane/surge model Validated hurricane/surge model Ran hundreds of hypothetical storms Computed return periods for study area Resulting storm surge still water elevations for the 1%- annual-chance event (ACE) 31

32 Modeling Part 2 Overland Waves 32

33 Limit of Moderate Wave Action (LiMWA) FEMA Procedure Memorandum No. 50, 2008 At present not a regulatory requirement No Federal insurance requirements tied to LiMWA CRS benefit for communities requiring VE zone construction standards in areas defined by LiMWA or areas subject to waves greater then 1.5 feet 33

34 Primary Frontal Dune (PFD) a continuous or nearly continuous mound or ridge of sand with relatively steep seaward and landward slopes immediately landward and adjacent to the beach and subject to erosion and overtopping from high tides and waves during major coastal storms NFIP regulations 34

35 Wave Runup Modeling and Mapping 35

36 Combined Probability - Mapping 37

37 Combined Probability Mapping (Cont d) 38

38 WHAFIS and Mapping 39

39 Duval County Transects 40

40 WHAFIS and Mapping 41

41 Work Maps - Example 42

42 Work Maps Example (Cont d) 43

43 Changes Since Last FIRM - Example 44

44 Upcoming Schedule 45

45 Timeline for Implementation SSAU Meetings Held: Complete Flood Risk Review Meetings Held: September 2015 Preliminary FIRMs and FIS Reports Delivered: November/December 2015 CCO Meetings and Flood Risk Open Houses Held: January Day Appeals Periods Started: March 2016 Letters of Final Determination Issued: October 2016 FIRMs and FIS Reports Distributed: December 2016 Resilience Meetings Held: December 2016 FIRMs and FIS Reports Effective: April

46 47

47 Open Discussion 48

48 Coastal Flood Risk Study Contacts Mark Vieira, PE (770) Christina Lindemer (770) Michael DelCharco, PE (904) Chris Mack, PE, PMP (843)