A hybrid, empirical radar wave inversion technique that treats swell and wind waves separately is presented and evaluated using a single 48-MHz radar unit and in situ wave measurements. This hybrid approach greatly reduces errors in radar wave inversion during swell seas. Our analysis suggests that, prior to the inversion, the second-order spectrum should be normalized using Barrick’s weighting function because this process removes harmonic and corner reflection peaks from the inversion and improves the results. In addition, the resulting calibration constants for the wind wave component are not wave-frequency dependent and are similar in magnitude to those found in previous studies using different operating-frequency radars. This result suggests radar frequency independence, although additional experimental verification is required. The swell component of the model presented here ignores the effect of swell’s propagation direction on the radar signal. Although this approach has several limitations and may only be useful near the coast (where swell propagates close to perpendicular to the coastline), the resulting wave inversion is accurate even when swell is propagating close to perpendicular to the radar beam direction. RMS differences relative to in situ wave height measurements range from 0.16 to 0.25 m as the radar beam angle increases from 22° to 56°.

Coastal wetlands protect communities during hurricanes by reducing storm surge flooding and damages. Previous studies have quantified surge reduction benefits of wetlands, but there is less understanding of how the combination of wetland loss and coastal development influences the spatial distribution of flood extents and damages. In this study we integrate a high-resolution 2-D hydrodynamic model with land-use/land-cover change analyses to assess the effects of total wetland loss, decadal wetland loss, and coastal development on storm surge damages in Galveston Bay, Texas. We measure storm surge flood extents from Hurricane Ike for three scenarios: (i) 2008 Baseline; (ii) 2008 No Wetlands, and (iii) 2019 “Present-day H. Ike”. We find that during Hurricane Ike in 2008, the total loss of coastal wetlands would have increased damages by a net ~ USD $934 million or 12.8% of baseline damages. For the 2019 Present-day H. Ike scenario, we found very few wetlands were lost between 2008 and 2019. If Hurricane Ike had occurred in 2019, damages would have been higher by ~ $2.52 billion or 34.6%, almost entirely due to increased real estate value and new coastal development. Our findings suggest that, while increase in economic exposure is a key driver of storm surge risks in Galveston Bay, effective wetland conservation continues to reduce these risks.

An examination of the applicability and accuracy of the empirical wave inversion method in the presence of swell waves is presented. The ability of the method to invert Doppler spectra to wave directional spectra and bulk wave parameters is investigated using one-month data from a 12 MHz WERA High Frequency (HF) radar system and in-situ data from a wave buoy. Three different swell inversion models are evaluated: LPM (Lipa et al. 1981), WFG (Wang et al. 2016) and EMP, an empirical approach introduced in this study. The swell inversions were carried out using two different scenarios: (1) a single beam from a single radar site and two beams from a single radar site, and (2) two beams from two sites (a single beam per site) intersecting each other at the buoy location. The LPM method utilized using two beams from two different sites was found to provide the best estimations of swell parameters (swell height RMS error 0.24m) and showed a good correlation with the partitioned swell in-situ values. For the wind wave inversion, the empirical method presented here is used with an empirical coefficient of 0.3 which seems to be suitable for universal application for all radar operating frequencies. The inverted swell parameters are used to create a swell spectrum which is combined with the inverted wind wave spectrum to create a full directional wave spectrum. The wave inversion method presented in this study although empirical does not require calibration with in situ data and can be applied to any beam forming system and operating frequency.