hurricane hazard information for caribbean coastal construction 1 hurricane hazard data for...

Hurricane Hazard Information forCaribbean Coastal Construction 1

Hurricane Hazard Datafor

Caribbean Coastal Construction

Project Overview

Funded by the Caribbean Regional Program of the US Agency for International Development.Executed by the Organization of American States, in conjunction with the

Engineering Institute of the University of the West Indies.

System Design and Analysis by Watson Technical Consulting.


Introduction

Project Goals

Storm Hazard Assessment Methodology

Statistical Methodology

Data Bases

On-line Data Access System


Project Goals

To create an easy to use on-line resource to allow planners and coastal engineers to access basic hurricane hazard data in a formatconducive for use in the design process.

Hazards reported are wind, wave, and storm surge, for 10, 25, 50, and 100 year return periods. Return period data is characterized at maximum likelihood (MLE), 75%, 90%, and 95%projection limits.

Two Web Sites to be established:Primary: University of the West IndiesBackup: Old Dominion University


Storm Impacts at the Coast

MeanLow Water

Pressure Setup

Wind Setup

Astronomical Tide

Wave Setup

Wave Run up

Still Water Level at Shoreline

Wave Crest/TWL

Three phenomena output: Wind, Waves, and Storm Surge.Storm surge outputs include of wave setup, wind setup, pressure setup, and astronomical tide.

Wind


Methodology Overview

Simulate every Atlantic storm since 1886 (1851) with the TAOShazard modeling system to generate the wind, wave, and storm surge at every grid cell in the study area.

At each point, compute weibull distribution for each phenomena.

Simulate return period events to test interactions.

Compute desired return period and projection limit results.


The Arbiter Of Storms (TAOS) hazard model

Modular, 4D composite model platform with user selectable modules:12 Wind Models3 Boundary Layer Models3 Storm Surge Models5 Wave Models2 Rainfall/Runoff Models

- 1,620 basic combinations- with damage functions, over 10,000 possible outcomes for a single event!

Scalable, from single processor through supercomputer MPI orPVM systems such as the WTCI earthdome system.

TSAP Statistics System with plug in modules for various distributions, either desktop of batch run capability.


Storm Hazard Model Modules

Key TAOS/mpi Modules:

•Wind Field

•Water Flow (Storm Surge)

•Waves

•Tides (UTex CSR Model)

•Rainfall and runoff

•DamageStructure DamageCoastal ErosionVegetation Damage

•GIS/Mapping InterfaceGrADS Meteorology packageArcInfo and ArcViewMapinfoGRASS

Storm components are interactive and can have feedbacks: for example, changes to land cover cause changes to wind speeds, etc.


Input Data Bases for Simulations

•Digital Elevation Model (topography and bathymetry)Allows proper flow of water to be computedfor storm surge, waves, and inland flooding

•Land Cover/Land Use (land and underwater)Friction effects on both air and water to computecorrect wind speeds and flow ratesDebris generation

•Historical Storm Characteristics for Statistical Analysis and validation


Model Physics: Wind

Module Used: Standard Project Hurricane (SPH)Source: NOAA Technical Report NWS 23

Basic wind field characteristics:Asymmetric wind fieldRadius of Maximum WindsStorm motionCentral and Far Field Pressure

Terrain effects: The wind at a point depends onwhat is upwind of the point, as much as 10 miles.

Note storm centered grid system.


Wind Model Validation Example

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Reported

Comparison of observed and computed peakwinds for Hurricane Floyd (1999)

Correlation: 0.9222


Model Physics: Storm Surge

Modules, vertical coordinates (3D vs. 4D), horizontal resolutionsdepends on underlying data bases

Low Res (> 600 meter grids): vertically integrated equationsSource Equations: Harris

High Res (< 600 meter grids): 5 vertical layersSource Equations: Watson, based on Mellor

Tides: University of Texas CSR Tide Model


Comparisons with Tide Gauges

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St. Augustine

Trident Pier

Solid Line: ModeledDots: Observed


Peak Surge Observations (Marilyn, 1995)Storm Source Location Type Observed Modeled %error Error (m)Marilyn 95 USGS SC 1 OB 0.98 1.00 2.50% 0.02

SC 2 OB 2.65 2.50 5.75% 0.15SC 3 OB 2.90 2.50 13.68% 0.40SC 4 OB 1.77 1.50 15.17% 0.27SC 5 OB 1.52 1.50 1.60% 0.02SC 6 OB 1.52 1.50 1.60% 0.02SC 7 OB 1.89 1.75 7.42% 0.14SC 8 OB 1.43 1.75 22.13% 0.32SC 9 OB 2.04 2.00 2.09% 0.04SC 10 OB 1.98 2.00 0.92% 0.02SC 11 OB 1.59 1.80 13.54% 0.21SC 12 OB 1.83 1.80 1.60% 0.03SC 13 OB 2.59 2.20 15.11% 0.39SC 14 OB 3.57 2.80 21.50% 0.77SC 15 OB 2.90 2.50 13.68% 0.40ST 1 OB 2.01 2.00 0.61% 0.01ST 2 OB 2.16 2.00 7.61% 0.16ST 3 OB 2.16 2.20 1.63% 0.04ST 4 OB 2.32 2.20 5.05% 0.12ST 5 OB 2.26 2.20 2.49% 0.06

Average: 0.18

Marilyn Storm Surge y = 0.6741x + 0.567

R2 = 0.9003

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Observed

Co

mp

ute

d

Observed peak water levels frompost storm surveys on St. Croix and St. Thomas by the USACE


Model Physics: Waves

NOAA Wavewatch III Model (deep and transitional water)Source: Tolman, modularized and modified for

moving grid

WTC inshore model (shallow water)Sources: Lyons, Watson

Again, physics used depends on resolution.


Wave Validation

Comparison of operational (real time) wave forecastand NOAA buoy reports


Validation Summary

Tests against detailed data from over 30 storms worldwide.

Performance summary (90% limits)Peak Wind (350 observations): +/- 5 knotsPeak Wave (185 observations): +/- 0.8 meters (deep water Hs)Peak Storm Surge (1500 observations): +/- 0.3 meters

Model uncertainty is included in the projection limit calculations.


Statistical Terminology

MLE: Maximum Likelihood Estimate. The ‘best guess’ at a value. Thisis NOT the same as the 50% estimate.

Projection Limit: For a given projection limit, the value which shouldnot be exceeded more than 1-(limit) of observations.

Example: 100 year, 75% projection limit.For a large number of 100 year periods, 75% of them will fallat or below this value. Only 25% should be greater.OR, for a large number of sites over a 100 year period, 75%of the sites will see less than this value; 25% would be expectedto exceed it.


Statistical Analysis

Once storm runs are completed, outputs are analyzed to producereturn period data sets.

Single Site Example: Four Seasons Hotel, Nevis


Single Site Analysis: Wind

BASIC TC WIND STATISTICS REPORT FOR Nevis

1220 EVENTS EXAMINED FROM 1850 TO 1999

NOTES: RAW DATA IS IN FILE YRMAX.DAT CAT 0 = TROPICAL STORM

EVENTS BY CATEGORYSAFFIR/SIMPSON CATEGORY 0: 48SAFFIR/SIMPSON CATEGORY 1: 9SAFFIR/SIMPSON CATEGORY 2: 4SAFFIR/SIMPSON CATEGORY 3: 1SAFFIR/SIMPSON CATEGORY 4: 1SAFFIR/SIMPSON CATEGORY 5: 0

------------------------------------------------ EMPIRICAL ESTIMATE OF RETURN PERIODSSAFFIR/SIMPSON CATEGORY 0: 2.5 YEARS 0.396SAFFIR/SIMPSON CATEGORY 1: 8.3 YEARS 0.121SAFFIR/SIMPSON CATEGORY 2: 24.8 YEARS 0.040SAFFIR/SIMPSON CATEGORY 3: 74.5 YEARS 0.013SAFFIR/SIMPSON CATEGORY 4: 149.0 YEARS 0.007SAFFIR/SIMPSON CATEGORY 5: Infinit YEARS 0.000

2 PARAMETER WEIBULL ESTIMATE OF RETURN TIMES

ALPHA 1.333316, BETA 35.105717SDA 0.21 SDB 4.40, CORREL: 0.871427

CHI**2 13.486692K-S 0.046980, K-S PROB 0.995793

5 YEAR WIND 50KTS (EMP: 52KTS) 10 YEAR WIND 65KTS (EMP: 70KTS) 25 YEAR WIND 84KTS (EMP: 79KTS) 50 YEAR WIND 97KTS (EMP: 89KTS)100 YEAR WIND 110KTS (EMP: 91KTS)

MLE BASED WIND RETURN TIMESWIND SPD PROB RETURN PD 50KTS 0.2014 5.0 YRS 64KTS 0.1078 9.3 YRS 100KTS 0.0176 56.7 YRS ------------------------------------------------ PROJECTION LIMIT CONFIDENCE LEVELS

YEAR 50% 75% 90% 95% 99% 10YR: 66.4 69.0 71.4 73.2 76.8 25YR: 85.3 89.3 93.5 96.9 108.8 50YR: 98.5 104.1 110.8 116.7 132.7100YR: 110.7 118.9 128.7 136.8 157.3

Raw text output of TSAP program:


Single Site Statistics: Nevis Wind

Graphic output ofweibull fit for windsat Four Seasons, Nevis


Statistical Methodology Validation

Used data from 1886-1987 to make a 10 year forecast.

Validated wind forecast against 10,600 land sites in the Atlantic Hurricanebasin using the 10 year period 1988 - 1997.

Percentage of sites below prediction limit:

Predicted Observed50% 53%75% 75%90% 90%95% 94%99% 97%


The Caribbean Hazard Data Web Server

Temporary URL:http://weather.methaz.com/cdcm/

Permanent URL:UWI: ??ODU: http://cdcm.cee.odu.edu/

Primary site will provide formailing lists to discuss coastalengineering and design problems,techniques, etc.

Interactive, web based system using open source/public domain software.


On-line Documentation

• Notes on wind, wave, and storm surge model outputs• Validation and uncertainty• Terminology• Building Code Notes


Available Data Bases

Regional 30 arc second (nominal 926 meters)As part of the Caribbean Disaster Mitigation Project (CDMP), a regional storm risk atlas was developed. The return period was based on an analysis of hurricanes from 1886 to 1998, with storm hazard model runs conducted using a regional 30 arc second (nominal 926 meter) grid. It covers the Eastern Caribbean from Puerto Rico through Trinidad and Tobago.

6 arc second (182 meter) Kitts/Nevis/Antigua/BarbudaThis data set was developed for the Post Georges Disaster Mitigation Project. It covers the islands of St. Kitts, Nevis, Barbuda, and Antigua. The return period analysis was based on data from 1851 through 1999. The storm hazard model runs were made at a resolution of 6 arc seconds (182 meter grid).Only MLE data available for this area.

Hurricane Track Data BaseThis is a version of the 1851-2000 storm track data set created by from the US National Hurricane Center.


Data Set Access

• User may select return period and projection limit• Choice of background maps• Point and click report generation


Report Format

Site Map and Data Location

Site information

Hazard Data


Summary

• On-line hurricane hazard data for the Eastern Caribbean• 10, 25, 50, 100 year return period data bases• MLE, 75%, 90%, and 95% projection limits for regional data set• R&D site available at http://weather.methaz.com/cdcm/• Final data sets and user interface by end of September 2001• Final web sites at UWI and ODU by end of 2001

hurricane hazard information for caribbean coastal construction 1 hurricane hazard data for...

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