Rapid population growth, urbanization, and concentration of valuable assets and strategic infrastructure in coastal regions make coastal inundation, flooding, and storm surge national problems for many countries, including theUnited States of America (USA). Enhancing coastal resilience is a complex problem and involves an integrated risk management approach, entailing both structural protection as well as other risk reduction strategies (e.g., building codes and ecosystem preservation). The former is an increasingly recognized mitigation option for densely populated areas and industrial hubs. Fully justifying benefits of costly flood defense structures is crucial, particularly when lack of funding and other institutional barriers make such projects easy targets for omission from or cuts to a budget. Justification usually requires a comprehensive cost-benefit analysis. This paper explores the economic feasibility of a coastal barrier, i.e., coastal spine, as a potential storm surge mitigation strategy to protect the Houston-Galveston metropolitan area of Texas, one of the most flood-prone and economically important regions in the USA. We provide an assessment of residential and chemical manufacturing plant and refinery exposure to multiple synthetic hurricane storm surge events by comparing losses with and without a coastal spine. While under all scenarios, benefits exceed engineering costs of a spine, our results indicate that the project feasibility largely hinges on accounting for industrial losses and resultant indirect and induced effects. As many regions and industrial hubs globally are designing adaptation and mitigation strategies to combat the consequences of extreme events, structural solution to surge mitigation maybe one of the few mitigation options for them. Unlike population and residential structures that can retreat and insure, these options are not viable for industrial plants that are resource-based. However, expertise and knowledge pertinent to surge barrier systems are relatively scarce as there are only handful of barriers around the world and they are all unique in engineering designs. As storm surge is becoming a threat for many coastal urban centers, one of the recommendations is to consolidate knowledge base and research across countries in order to foster knowledge exchange internationally. This will help identify concerns associated with existing barrier systems, pragmatic ways to improve them and will also aid the investment decision, engineering designs, and operational aspects of barriers in other parts of the world. Furthermore, forming regional research collaborations with developing countries at risk of storm surge and the sea level rise is vital to further facilitate knowledge spillover and exchange of expertise.

This chapter describes the processes that generate storm surge and waves, the role of each process in coastal flooding and loadings on structures, the factors that influence spatial and temporal variability in waves and water levels, and the methods for characterizing both for analysis and design. Wind and, to a lesser degree, spatial gradients in atmospheric pressure and momentum fluxes associated with waves generate storm surge, particularly in the surf zone. Hydrostatic loads are associated with the storm water level and changes in water surface elevation induced by waves; hydrodynamic loads are associated with the force of moving water, including the effects of waves. Hurricane characteristics include track, intensity, size, and forward speed. Hurricane storm surge and waves are characterized mostly through regional, basin-scale computer modeling, which can include the interactions between storm surge and waves.

: This report documents the methodologies used, procedures followed to generate wind, wave, and storm surge estimates for 150 preselected extreme storm events along the Lake Michigan coastline. These simulations provide a storm climatology spanning 60-years (1960 through 2009). Two methodologies are used to generate the wind and pressure fields for the Lake Michigan region. The NOAA/NCEP Climate Forecast System Reanalysis, a 30-year (1979 through 2009) archive data set providing gridded wind speed, direction and sea level surface pressure fields. The second being the Natural Neighbor Method developing necessary fields from point source meteorological stations on a fixed grid system (1960 though 1978). Archived ice concentration fields were applied to the extreme storm events occurring during the winter months. The WAM model and STWAVE are used to describe the wave climate; ADCIRC is used to estimate the surge. The models are rigorously evaluated for a pre-selected storm population, using both wind field methodologies and compared to existing data sources (winds, waves and water levels). Upon completion of this evaluation phase, the 150-extreme storm events are simulated and evaluated at gage sites, for the entire coastline of Lake Michigan.

Coupled storm surge simulations with fine resolution have become a reality due to the rapid development of computer power and advancement in the integration of the simulation models. However, the real-time application of such robust simulations is often constrained by the availability of time and computational resources. In this study, an alternative, Storm Surge Forecasting Tool (SSFT) has been developed to forecast storm surge in Coastal Mississippi. The algorithm of SSFT uses a weight based Storm Similarity Index (SSI) that is defined by current hurricane position Central Pressure (CP), Pressure Scale Radius (Rmax) along with hurricane track, landfall location, storm forward speed, and forecasted storm track published by the National Hurricane Centre (NHC) and correlated with the characteristics of synthetic storms within the underlying database. Based on the values of SSI (scales from 0 to 1), the SSFT identifies a group of storms that much as close as possible with the characteristics of the approaching hurricanes and then display high resolution simulation results (e.g., maximum surge elevation and hydrographs). The SSFT model operates in two different modes:1) Hindcasting mode and 2) Forecasting mode. The SSFT GUI was tested in both modes and we found that the method is very promising. Using this tool and approach as a decision aide, the emergency personnel can quickly forecast local storm surge along the coast of Mississippi. This will allow them to make quantitative and objective decisions by evaluating "what-if-scenarios† starting two to three days ahead of the landfall.

A coupled system of wind, wind wave, and coastal circulation models has been implemented for southern Louisiana and Mississippi to simulate riverine flows, tides. wind waves. and hurricane storm surge in the region. The system combines the NOAA Hurricane Research Division Wind Analysis System (H*WIND) and the Interactive Objective Kinematic Analysis (IOKA) kinematic wind analyses, the Wave Model (WAM) offshore and Steady-State Irregular Wave (STWAVE) nearshore wind wave models, and the Advanced Circulation (ADCIRC) basin to channel-scale unstructured grid circulation model. The system emphasizes a high-resolution (down to 50 m) representation of the geometry. bathymetry, and topography nonlinear coupling of all processes including wind wave radiation stress-induced set up; and objective specification of frictional parameters based on land-cover databases and commonly used parameters. Riverine flows and tides are validated for no storm conditions, while winds, wind waves, hydrographs, and high water marks are validated for Hurricanes Katrina and Rita.

Hurricanes Katrina and Rita were powerful storms that impacted southern Louisiana and Mississippi during the 2005 hurricane season. In Part I, the authors describe and validate a high-resolution coupled riverine flow, tide, wind, wave, and storm surge model for this region. Herein, the model is used to examine the evolution of these hurricanes in more detail. Synoptic histories show how storm tracks, winds, and waves interacted with the topography, the protruding Mississippi River delta, east-west shorelines, manmade structures, and low-lying marshes to develop and propagate storm surge. Perturbations of the model, in which the waves are not included, show the proportional importance of the wave radiation stress gradient induced setup.

Experiments were conducted in the Large-scale Sediment Transport Facility (LSTF) at the U.S. Army Engineer Research and Development Center to investigate the importance of wave height, period, and breaker type (spilling and plunging breakers) on total rate of longshore sediment transport (LST) and the cross-shore distribution of LST. Estimates computed by the CERC formula and Kamphius were compared to the accurately measured total LST rates. Several K-values were used with the CERC formula, including the recommended value of 0.39 and calculated values by Kamphuis and Readshaw, Ozhan, Bailard, and Del Valle et al. The recommended K-value and most of the calculated K-values overpredicted the measured total LST rates, but methods that included parameters to indicate breaker type gave good estimates. The Kamphuis and Readshaw equation, in which K is a function of surf similarity parameter, gave consistent estimates with measurements. The Kamphuis equation, which includes wave period and beach slope that in turn influences wave breaking, also compared well with the measurements. Additionally, the CERC formula has been used successfully if K is calibrated, and the formula gave excellent results if K was calibrated with measured data and applied to similar breaker types. The findings indicate that total LST rate is strongly influenced by breaker type. The cross-shore distribution of LST indicated three distinct zones of transport: the incipient breaker zone, the inner surf zone, and the swash zone. Transport in the incipient breaker zone was influenced by breaker type. Transport in the inner surf zone indicated that wave height was the dominating factor and independent of wave period. Swash zone transport, which accounted for a significant percentage of the total transport, showed a dependence on wave height, period, and beach slope.

The purpose of this investigation was to examine storm surge and wave reduction benefits of different environmental restoration features (marsh restoration and barrier island changes), as well as the impact of future wetland degradation on local surge and wave conditions. Storm surge simulations of two representative hurricanes were performed using the ADCIRC storm surge model with the inclusion of radiation stress gradients from the STWAVE nearshore wave model. Coupled model simulations were made for a number of landscape configurations that involved both restored and degraded wetland features. The impact of barrier island condition on hurricane surge and waves was also evaluated. Effects of landscape features were represented by changes in elevation and frictional resistance. Restoration and degradation of marsh resulted in decreases (for restoration cases) and increases (for degradation cases) in both surge and waves. The magnitude of change was correlated with the magnitude of the horizontal extent and elevation changes in the marsh. In general, the wave change patterns are consistent with the water level changes. Deflation of the Chandeleur Islands (barrier island chain) resulted in slightly increased surge. Results suggest that coastal marsh does have surge and wave reduction potential. Results also indicate that the impact of the landscape features is amplified in areas where there are levee “pockets.” Barrier islands and coastal ridges reduce wave heights, even if in a degraded condition and thus can reduce wave energy in wetland areas, protecting them from erosion.

Hurricane Katrina caused devastating flooding in St. Bernard Parish, Louisiana. Storm surge surrounded the polder that comprises heavily populated sections of the Parish in addition to the Lower 9th Ward section of Orleans Parish. Surge propagated along several pathways to reach levees and walls around the polder's periphery. Extreme water levels led to breaches in the levee/wall system which, along with wave overtopping and steady overflow, led to considerable flood water entering the polder. Generation and evolution of the storm surge as it propagated into the region is examined using results from the SL15 regional application of the ADCIRC storm surge model. Fluxes of water into the region through navigation channels are compared to fluxes which entered through Lake Borgne and over inundated wetlands surrounding the lake. Fluxes through Lake Borgne and adjacent wetlands were found to be the predominant source of water reaching the region. Various sources of flood water along the polder periphery are examined. Flood water primarily entered through the east and west sides of the polder. Different peak surges and hydrograph shapes were experienced along the polder boundaries, and reasons for the spatial variability in surge conditions are discussed.

The Louisiana Coastal Protection and Restoration (LaCPR) study was authorized by the U.S. Congress to develop a range of flood control, coastal restoration, and hurricane protection measures to make South Louisiana more resilient to hurricane risk. This article briefly describes the approach and integrated modeling system applied to estimate surge and waves. The effect of proposed project alternatives on storm surge levels and waves had to be examined over large spatial and temporal scales for the LaCPR study. A regional surge and wave model was developed to meet this requirement. The modeling system developed has unprecedented detail and captures the important scales of motion for hurricane storm surge inundation and waves. Both natural features and man-made structures can be appropriately represented, which allows for a regional, holistic approach to the evaluation of storm surge and wave mitigation where both engineered and natural features are considered. The computed surge and waves provided input for the hydraulic analysis, which applied frequency curves computed with a modified Joint Probability Method (JPM) referred to as the JPM with Optimal Sampling (JPM-OS). The computed exterior frequency curves were used to determine required levee heights and estimate interior stage frequency curves for calculating damages. Sample surge results are presented which indicate that proposed protection alternatives can impact water levels regionally and that wetland loss may result in increased surges at some locations along the coast.

This paper discusses the value of a community approach to characterizing the coastal storm hazard, e.g., hurricane water levels and wave conditions, through field measurements, data analysis, and modeling. Value is illustrated using experiences and results from recent and ongoing projects. One example is recently completed work by the Interagency Performance Evaluation Task Force (IPET), which was commissioned by the U.S. Army Corps of Engineers. The IPET was charged with gathering the facts regarding performance of the hurricane protection system in Southeast Louisiana in response to Hurricane Katrina. A second example is ongoing work being lead by the Corps to design projects that can greatly reduce the likelihood and consequences of flooding for coastal Louisiana and Mississippi. These investigations are being closely coordinated with work of the Federal Emergency Management Agency to update flood insurance rate maps for the region. Findings and lessons learned are discussed, and challenges in making accurate surge and wave predictions are identified, including: 1) inaccuracy in coastal and estuarine wind fields, 2) specification of a wind drag law in shallow coastal areas, and 3) problems in treating nearshore wave set-up and coupling into surge models. A new Corps research program that is addressing many of these issues, also a community effort, is described as are results from early progress in selected problem areas. The paper presents advantages to developing open-source, community-based computer software for coastal storm wave and surge predictions, and some problems with today's over-reliance on proprietary software.

: The U.S. Army Engineer Research and Development Center (ERDC) performed a number of engineering studies in support of U.S. Army Engineer District, Mobile (SAM) efforts to develop a Dredged Material Management Plan (DMMP) for the Federal navigation project at Pascagoula, MS. The studies focused on evaluating an option under consideration for the placement of dredged material in an island confined disposal facility (CDF). Numerical modeling of circulation, water quality, and wave climatology were performed to examine the potential impacts of an island CDF, and for engineering design considerations. Field measurements of currents and waves in the Mississippi Sound were made. A number of studies were performed to examine the sediment consolidation process in the CDF with the primary objective of assessing its dredged material volume capacity. Quantitative and qualitative studies results were produced for three alternative locations. The three locations are an island CDF just northeast of Round Island and southeast of the Singing River, between Round Island and the main navigation channel leading to Horn Island Pass and the Gulf of Mexico, and north of the point where the main navigation channel biflircates to service the Pascagoula River and Bayou Casotte Harbors.

PURPOSE: Accurate predictions of the total rate of longshore sand transport (LST) and its cross-shore distribution pattern in the surf zone are central to many coastal engineering studies. Present understanding and methods for calculating the LST rate are largely developed based on field studies (e.g., Komar and Inman 1970; Inman et al. 1981; Kraus et al. 1982; Bodge and Dean 1987a, b; Dean 1989; Schoonees and Theron 1993; Miller 1998; Wang, Kraus, and Davis 1998; Wang 1998; Wang and Kraus 1999; Miller 1999). The Coastal Engineering Research Center (CERC) formula (Shore Protection Manual 1984), which is based on field measurements, is often used to calculate the total LST rate. Accuracy of the CERC formula is believed to be ± 30-50 percent and several parameters that logically might influence LST are excluded in the formula, such as breaker type and grain size. The GENESIS shoreline change model, a tool commonly used in shore protection and beach-fill project design, utilizes the CERC formula. In the GENESIS model, the cross-shore distribution of LST is assumed to be uniform across the surf zone. Laboratory data (Bodge 1986; and Kamphuis 1991) and field data (Zenkovitch 1960; Ingle 1966; Bodge and Dean 1987a, b; Miller 1998) suggest that the distribution is not uniform. This technical note summarizes results of initial experiments conducted in the new Large- scale Sediment Transport Facility (LSTF) (see Fowler at al. 1995; Hamilton and Ebersole 2001 for additional details about the LSTF). Experiments are underway to investigate the importance of breaker type (spilling and plunging breakers) on LST, to examine the accuracy of presently used methods for calculating the total LST rate, and to aid in developing improved predictors for both the total LST rate and its cross-shore distribution patterns for varying surf conditions. Initial results concerning the cross-shore distribution pattern for the two different types of breaking waves are also presented. The LTSF experiments are intended to span the gap between laboratory measurements and low-energy field measurements. The LSTF is capable of simulating wave conditions that are almost directly comparable to annual averages along many low-wave-energy coasts, for example a majority of estuarine beaches (Nordstrom 1992) and many beaches along the Gulf of Mexico and the Great Lakes in the U.S. BACKGROUND: A commonly used tool for predicting the total rate of longshore transport is the CERC formula (Shore Protection Manual 1984),

The wave transformation model STWAVE was applied to calculate wave heights and directions at the entrance to Willapa Bay. The model was driven with input waves from an offshore buoy and compared to nearshore pressure gauge measurements. Including current in the bottom pressure gauge analysis for Willapa had a significant impact on wave height estimates (neglecting current resulted in up to 20% overestimates of wave height during flood current). Verification results showed reasonable agreement between calculations and measurements (root-mean-square (RMS) errors in wave height of 0.1–0.3 m and RMS errors in direction of 7–15 deg). The dominant transformation process for waves in the bay was wave breaking over the Willapa bar. The dissipation is controlled by the tide elevation over the bar. Wave-current interaction is significant only in the outer Willapa entrance channel where currents reached 2 m/sec. Wave heights on ebb increased up to 80 percent and on flood decreased up to 20 percent.