Comparison of Wave Climate Analysis Techniques in Sheltered Waters May 19, 2011 Tim Hillier, P.E.,...
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Comparison of Wave Climate Analysis Techniques in Sheltered Waters May 19, 2011 Tim Hillier, P.E., CFM Associate Lauren Klonsky Water Resources Engineer
Comparison of Wave Climate Analysis Techniques in Sheltered
Waters May 19, 2011 Tim Hillier, P.E., CFM Associate Lauren Klonsky
Water Resources Engineer
Slide 2
Coastal Models: A Value Added Proposition Objective: Engender
an open discussion regarding the perceived and technical
significance of hydrodynamic models for coastal flood hazard
studies. What is the relative precision as compared to analytic
methods? What is the level of precision required for flood
insurance studies? Where is the tipping point? ASFPM 2011
Slide 3
Coastal Models: A Value Added Proposition What this
presentation does NOT do: Validate or negate specific models
Recommend a singular study approach for FEMA studies Propose that
hydrodynamic models are not necessary ASFPM 2011
Slide 4
Purpose of Coastal Flood Hazard Studies Deliver quality data
that increases public awareness and leads to action that reduces
risk to life and property ASFPM 2011
Slide 5
History of Coastal Floodplain Mapping 1968 1973 1977 1979 1981
1986 to 1988 1988 1989 1995 2002 2005 2007 NFIP Authorized H b = 3'
NAS Develops Wave Analysis Methodology FEMA Adopts NAS Methodology
Runup Methodology Accepted Wetland Vegetation Muddy Bottom Erosion
Analysis (540SF) PFD CERC TR 89-15 G&S for Wave Elevation and V
Zone Mapping Appendix D Proc. Memo No. 37 Atlantic Ocean and Gulf
of Mexico Guidelines Update (Final Draft) ASFPM 2011
Slide 6
History: Coastal Modeling Development Lewis Fry Richardson
(1920s) 6 hour forecasts for two points; 6 weeks LOE Computer
Simulations (1950s) Rossby (1954) Joint Weather Prediction Unit
(1955) Norman Phillips (1956) First successful climate model NOAA
Geophysical Fluid Dynamics Laboratory (late 1960s) Development of
Regional Models (1970s/1980s) Effects of soil/vegetation Advanced
Circulation Model (1990s) Luettich and Westerink ASFPM 2011
Slide 7
History: Coincidence of FIS and Models Synthetic Northeaster
Model (1978) Simple Model Development (Mid-1980s) WHAFIS RUNUP 1-D
Routing Routines (DYNLET) FEMA Surge (1988) Advent of
Two-Dimensional Models (1990s) Water Surface Wave Climate Sampling
Techniques (late 1990s to Present) EST JPM and JPM-OS ASFPM
2011
Slide 8
Benefits of Hydrodynamic Models: Technical Provides a numerical
description of a system by which the investigator can observe the
impacts of variable inputs on the system Ability to characterize
multiple events based on limited localized input Hindcasting
Increase resolution of study domain ASFPM 2011
Slide 9
Benefits of Hydrodynamic Models: Perceived Second approach for
a typical appeal is to question the technical validity of the study
techniques Getting into the weeds Literally Were the state-of-art
techniques used? Application of hydrodynamic models and associated
modeling routines is indicative of a fully detailed study ASFPM
2011
Slide 10
Limitations of Hydrodynamic Models Cost Calibration with
limited measured data Engineering decisions and Assumptions ASFPM
2011 Relationship of Accuracy to Cost Tipping Point
Slide 11
Limitations of Hydrodynamic Models Model data is used as input
to 1-D models WHAFIS Wave runup routines Coastal BFEs are mapped to
the whole foot Mapping Decisions Primary Frontal Dune Erosion
approaches Topography ASFPM 2011
Slide 12
Guidance for Sheltered Waters Guidance for Coastal Flood Hazard
Analyses and Mapping in Sheltered Waters (February 2008) Addresses
two study categories: New studies Existing studies under which
sheltered water bodies require additional assessment Transformation
vs. Generation Water Level Wave Conditions and Wave Setup Erosion
and Coastal Structures Overland Wave Propagation and Wave Runup
ASFPM 2011
Slide 13
Case Study: Plymouth Harbor ASFPM 2011 Ongoing study update for
Plymouth Harbor Extratropical events dominate 1991 Halloween
NorEaster Public relevance
Slide 14
Case Study: Plymouth Harbor ASFPM 2011
Slide 15
Case Study: Plymouth Harbor Study Approaches: Comparison of
wave climate analyses Offshore Inshore Numerical and Analytical
Techniques Steady State Wave Model (STWave) Automated Coastal
Engineering Software ASFPM 2011
Conclusions Decision to model has several considerations
Physical Characteristics Budget Perception Degradation of model
precision in translation to maps Calibration with measured
nearshore data ASFPM 2011