Introduction to Risk MAP NYC Coastal Study

Transcription

1 Introduction to Risk MAP NYC Coastal Study FEMA REGION II October 18, 2012 Alan Springett, Senior Engineer 1

2 Agenda Components of FEMA Region II Coastal Surge Analysis Overview of entire process at a glance ADCIRC model development Comparison to SLOSH Model inputs Topography/bathymetry Land use Field reconnaissance Storm characterization & selection JPM Statistics and Synthetic Tracks Wind pressure and field modeling Surge analysis ADCIRC model validation Wave setup and surge modeling Return period analysis WHAFIS and overland wave height Wave runup Coastal hazard modeling 2

3 Why Are We Here? EST Tide Gage JPM-OS-Q Empirical Track + JPM-OS 3

4 Why Are We Here? 4

5 What Was Done? November 1983 First detailed FIS of NYC (new 2 topography up to elevation 20) 1990 s Small revision to delete unnumbered A Zones in Staten Island & Queens 1990 s Two revisions to study several small streams in Staten Island by detailed methods 2007 Updated NYC DFIRM for purpose of digitizing 5

6 What Are We Doing? 5/31/13 New preliminary DFIRM new 2 LIDAR & new coastal hydraulics 19 coastal counties in NY and NJ 9 additional counties up the Hudson Valley 6

7 Models Numerical Models SLOSH OWI PBL Hurricane Model ADCIRC-UNSWAN Surge & Wave Model UNSWAN Model Significant Wave Heights and wind vectors predicted during Hurricane Dennis on the Basin Scale grid at 50 hours into the simulation. 7

8 Sea, Lake, and Overland Surges from Hurricanes (SLOSH) 8

9 Wind Model Comparison ADCIRC & SLOSH* ADCIRC Dynamic atmospheric model. Requires five input parameters: Central Pressure, po Background Pressure, pb Radius of Maximum Winds, RMW Maximum Wind Speed, Forward Velocity, Vf Multiple number of dynamic surface friction coefficients. SLOSH Simplified parametric model. Requires three input parameters: Central Pressure, po Background Pressure, pb Radius of Maximum Winds, RMW Limited number of static surface friction coefficients. No tidal interaction Not currently run for extratropical events *From Bailey, James R., PhD.,P.E. FSAR 2.4.5, Probable Maximum Surge and Seiche Flooding 9

10 ADvanced CIRCulation Model (ADCIRC) A (PARALLEL) ADVANCED CIRCULATION MODEL FOR OCEANIC,COASTAL AND ESTUARINE WATERS The ADCIRC source code is copyrighted, by R.A. Luettich, Jr. and J.J. Westerink A system of programs solving time dependent, free surface circulation and transport problems in two and three dimensions using finite element methods and unstructured grids. 10

11 Simulating WAves Nearshore (SWAN) Tight Coupling of SWAN + ADCIRC Solves the action balance equation: Models use same unstructured mesh; Information passed dynamically SWAN is as accurate as WAM and STWAVE Coupled model is efficient to 1000s of computational cores Communication is optimized for high-performance computing: 11

12 Coastal Surge Analysis Components Acquire map data and field reconnaissance Develop model inputs for topo/bathy grid, land use, etc. Characterize the local storm climate (tropical & extra-tropical) Develop method of forward projection Create surge heights with numerical models Analyze recurrence statistics Develop 0.2%,1.0%,2.0% & 10.0% surge heights with wave set-up WHAFIS overland wave conditions & BFEs 12

13 Coastal Study Technical Advisory Panel (TAP) Technical Advisory Panel (TAP) was established to engage coastal study subject matter experts Meetings were held on: 4/14/2011, 5/10/2011 and 11/10/2011 Some of the Members: Academics and Non-Profit Agencies: Jacques Cousteau National Estuarine Research Reserve (under Rutgers University) Richard Stockton College Coastal Research Center Monmouth University Urban Coast Institute Barnegat Bay National Estuary Program Sustainable Jersey, Climate Adaption Task Force State and Local Governments: New Jersey Department of Environmental Protection New York State Department of Environmental Conservation New York City (multiple departments: Office of Long Term Planning and Sustainability, Buildings and Planning) Other Federal Agencies: NOAA; USGS; USACE; 13

14 Surge Field Reconnaissance 14

15 Hurricane Measurements Period of Record Search & Capture Areas 15

16 Storm Selection for Synoptic Climatology Thirty storms selected for synoptic climatology 1938_04 NOTNAMED* 1944_07 NOTNAMED* 1948_03 NOTNAMED 1952_03 BAKER 1953_02 BARBARA 1953_04 CAROL 1954_03 CAROL 1954_05 EDNA 1954_09 HAZEL 1955_02 CONNIE 1958_04 DAISY 1960_05 DONNA* 1961_05 ESTHER 1967_04 DORIA 1969_07 GERDA 1972_02 AGNES 1976_03 BELLE 1978_06 ELLA 1985_07 GLORIA* 1990_02 BERTHA 1991_02 BOB 1993_05 EMILY 1996_05 EDOUARD 1996_08 HORTENSE 1999_06 FLOYD 2002_08 GUSTAV 2003_09 ISABEL 2004_01 ALEX 2007_16 NOEL 2009_03 BILL All candidate storms ( ; 236 storms, ~ 8,400 snapshots) * Used as AdCIRC/UNSWAN Verification Storm 16

17 Nor easter Storm Analysis Storm Dates (Y M/D) / / / / / / / / / / / / /29* / /31* /11* / / / / / / / / / / / / / /13 * Used as AdCIRC/UNSWAN Verification Storm 17

18 ADCIRC/SWAN Mesh Nodes: 604,790 Elements: 1,188,640 Min mesh size: 70 meters 1 second time step goal 18

19 ADCIRC/SWAN Mesh 19

20 Topography Data Sources NY NYC DOITT 3 ft DEM Westchester 2 FEMA compliant contours Hudson Valley USGS NED 1/3 arc second DEM 20

21 Bathymetric Data Sources NOAA Hydrographic Surveys National Geophysical Data Center Office of Coast Survey NOAA Navigation Charts Frequently provides data in areas where digital survey data is not available (fills gaps) USACE SHOALS/CHARTS Hydrographic LiDAR Limited coverage due to light penetration in the water column USACE District Surveys (Retrieved from NAN and NAP) Limited to Federal navigation projects or project specific study areas 21

22 Shoreline and Boundary Extraction Accurate shoreline essential for seamless DEM Other uses: Boundary (ADCIRC), WHAFIS, DFIRMS Extracted and corrected for each county Upper limits of flooding generated and extracted. 22

23 Probabilistic Model for Storm Characteristics Parameter Distribution Type Distribution Parameters P (mb) Truncated Weibull* U=41.2 K=2.05 Rp (km) Lognormal median=vickery-wadhera σ lnrp =0.44 (2008)** Vf (kt) Normal mean=6+0.4 P σ=7 θ (deg) Normal*** mean=22 (23 in LI) σ=10 B Normal mean=1.1 σ=0.2 * P[ P> x] = cexp[ ( x/ u) k ]; x> P(33mb) 0 **Eq. for median: *** truncated at 26 deg for NJ 23

24 JPM-OS1 storms (final* model) *Latitude-dependent P and Rp 24

25 Nor easter Storm Analysis Storm Dates (Y M/D) / / / / / / / / / / / / /29* / /31* /11* / / / / / / / / / / / / / /13 * Used as AdCIRC/UNSWAN Verification Storm 25

26 Summary of Storm Selection Hurricanes JPM-OS with 35 Synthetic Storms each on a set of approximately 6 to 9 tracks (depending on storm size) Consider only storms with DP> 33 mb (Cat > 2) Extra-tropical Storms 30 Historic storms 12 are significant 26

27 Next Steps Forward Modeling, Return Period Analyses and Wave Parameters for WHAFIS 27

28 Example Envelope of Maximum Compute Surge Heights 159 STORM SIMULATIONS (## STORM-TYPES) PARALLEL TRACK SETS (W/ LANDFALLS BEYOND AREA) RANDOM SEMI-DIURNAL TIDE PHASES 28

29 General Flow Chart for NY/NJ Production Runs 29

30 General Flow Chart for NY/NJ Production Runs Input Checks- File correct Scanning 30

31 General Flow Chart for NY/NJ Production Runs Input Checks- File correct Scanning Local Checks Files completion Initial MEOWs Initial time series 31

32 General Flow Chart for NY/NJ Production Runs Input Checks- File correct Scanning Local Checks Files completion Initial MEOWs Initial time series Full QA/QC MEOWs plots Time-series plots Animations Automated scripts 32

33 Inclusion of Astronomical Tide New York-New Jersey area; (a) Water elevation difference (meters) of ST minus S at time of maximum ST surge; (b) water elevation deviation (meters) from linear superposition with extrapolated tides. Black line is shoreline; brown line is the limit of the model mesh. 33

34 Sum Exceedance Frequencies for Each Value of Surge Height Annual Exceedance Frequency Combined Hurricane Extra-Tropical 0.046(H'cane)+0.038(N'easter)=0.084(total) Surge Height (m) 34

35 Composite Surge/Frequency Ranking Surge Wave Height Wave Period Surge Elevation (m) Wave Height (m), Period (s) Storm Rank (based on surge) 35

36 Transect Layout and Model Setup 36

37 Overland Feature Characterization Coastal hazard analysis and overland wave modeling require information on land cover and obstructions (buildings) within the study area. Dunes, buildings, plant types and their density control overland wave dissipation. 37

38 Coastal Structure Evaluation The presence of coastal structures along a section of shoreline can affect how erosion analyses are conducted. FEMA has specific guidelines on how to evaluate and treat coastal structures in coastal hazard analysis. 38

39 Erosion Methodology and Analysis FEMA guidelines and specifications define a standard erosion methodology for dunes (i.e., the 540 rule ). A review of the geology and shoreline types will be made to determine the applicability of standard erosion methods and determine the necessity of nonstandard approaches. 39

40 Wave Height Analysis for Flood Insurance Studies (WHAFIS) Wave transformation modeling will be conducted from the shoreline and overland using FEMA s WHAFIS model. The WHAFIS model has been used in Flood Insurance Studies since 1980 to incorporate the effects of wave action on FIRMs for communities along the Atlantic and Gulf Coasts. WHAFIS is a onedimensional model that will be applied to each transect in the Region II study area. The model uses a specified Stillwater Elevation (SWEL), and the starting wave conditions as input. Simulations of wave transformations are then conducted with WHAFIS taking into account the storm-induced erosion and overland features of each transect. Output from the model includes the combined SWEL and wave height along each cross-shore transect allowing for the establishment of BFEs and flood zones from the shoreline to points inland within the study area. 40

41 Wave Runup and Over-topping 1938 Long Island Express waves hitting seawall - Photo courtesy of NASA Wave runup is defined as the maximum vertical extent of wave uprush on a beach or structure. FEMA s 2007 Guidelines and Specifications require the 2% wave runup level be computed for the feature being evaluated (cliff, coastal bluff, dune, or structure). Each transect defined within the Region II study area will be evaluated for the applicability of wave runup. 41

42 Coastal Flood Hazard Mapping Coastal flood hazard mapping is the process where the overland wave modeling results are assimilated with the topography data to delineate the boundary of the Special Flood Hazard Area (SFHA) for the 1% annual chance stillwater elevation (100-year conditions), along with mapping the location and extent of Zones VE, AE, and X. 42

43 FIRM Production 43

44 Coastal Outreach Advisory Team (COAT) The Coastal Outreach Advisory Team was established to support the New Jersey and New York City Coastal Flooding Outreach and Education Program Technical Advisory Panel (TAP) is focused on technical aspects of the flood risk program 44

45 Introduction to Risk MAP NYC Coastal Study Questions? - Contacts Alan Springett, Senior Engineer, FEMA Region II Mitigation, Risk Analysis 26 Federal Plaza, Rm 1337 New York, NY Desk Mobile Alan.Springett@fema.dhs.gov J. Andrew Martin, CFM RSC II Lead Coordinator Dewberry Management & Consulting Services 15 East 26 th St, 7 th Floor New York, NY amartin@dewberry.com 45