Landuse Attributes for Overland Wave Modeling Paul Carroll, PE

Coastal Methodology Overview Storm surge modeling with the ADvanced CIRCulation Model (ADCIRC) Wave modeling with the WaveWatch III Model and the Simulating Waves Nearshore (SWAN) Model Overland wave analysis using FEMA’s Wave Hazard Analysis for Flood Insurance Studies (WHAFIS) Model Hazard Zone Mapping ADCIRC SWAN Water level, currents Wave radiation stress WHAFIS

Overland Wave Modeling Wave Height Analysis for Flood Insurance Studies – WHAFIS 1-D model – interfaced with GIS-type software allows for increased model transect density Capable of variable obstructions including vegetation types and buildings

Overland Wave Modeling 1-D Approach based on: Water depth Wave decay Wave regeneration

Overland Wave Modeling

Landuse Characterization Open or Inland Fetch Rigid Vegetation Buildings Marsh

Level of Effort to Appropriately Characterize a Vegetation Polygon Level of input detail should be commensurate with the ability of the model to reflect a change in Wave Height So how precise should values be……? Input data need to be regionally reflective So how useful are spot measurements……?

VE Categories and Testing Mean Spacing – Beyond 50-ft nominal impact

VE Categories and Testing Mean Spacing – Max delta of 1.0 across the sub-cat range

VE Categories and Testing Mean Trunk Diameter

Suggested Categories for Vegetated Tracts

Level of Effort to Appropriately Characterize a Building Polygon Level of input detail should be commensurate with the ability of the model to reflect a change in wave height Input data need to be regionally reflective

Locate modeling transects in regionally representative areas

Delineate areas of uniform building density

Transect is sub-divided into sections, wave computations are performed at each node

Typically 0 or 1 row of buildings within each segment

Attributing Modeling Transect Segments

Suggested Categories for Building Areas 90% 65% 40% 25%

Characterizing Landuse in mixed BU/VE areas

Elevated 100% Open On-Grade 65% Open On-Grade 65% Open Rigid Vegetation Inland Fetch (IF) Open Fetch (OF) 11/28/2018

Mapping Results Transect 2 Transect 3 Transect 1

References BakerAECOM, September 2010. DRAFT Task A.2.a, c., d., & e: Interim Report, Analysis of ADCIR Mesh Size and Resolution in Six Recent Coastal FISs and Requirements for a Northeast Florida/Georgia FIS. North Carolina Storm Surge Study. Dorman, John., Blanton, Brian., et. al. Atlantic Ocean and Gulf of Mexico Coastal Guidelines Update. FEMA , 2007.