RAPID DEPLOYMENT AND POST-STORM RECONNAISSANCE OF HURRICANE LAURA

Hurricane Laura made landfall on the southwest Louisiana coast near Cameron, LA on August 26th. As Laura approached the Louisiana coast, the Coastal Emergency Risks Assessment predicted a storm surge of approximately 5.2 m (17 ft), which marked the strongest surge to impact southwest Louisiana since the catastrophic Hurricane Rita in 2005. As a result, a team led by LSU and NEU mobilized to deploy surge and wave sensors and collect drone imagery at Rockefeller Wildlife Refuge and Cameron, LA on August 25th before the arrival of tropical storm winds. Rockefeller Refuge was selected to measure the capacity of wetlands and breakwaters to attenuate hurricane surge and waves, and pressure sensors were strategically placed at locations of civil infrastructure at Cameron to capture hurricane-induced overland flow (see Fig. 1). After the surge water receded, LSU retrieved the sensors, collected RTK elevation transects and multispectral drone imagery, and surveyed infrastructure damage along the southwest corridor of Louisiana, following the Highway 82 from Abbeville to Cameron.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/IevnFZ2YVfI

The Environmental Health Impact of Hurricane Katrina on New Orleans

Hurricane Katrina caused unprecedented flood damage to New Orleans, Louisiana, and has been the costliest hurricane in US history. We analyzed the environmental and public health outcomes of Hurricane Katrina by using Internet searches to identify epidemiological, sociodemographic, and toxicological measurements provided by regulatory agencies. Atmospheric scientists have now warned that global warming will increase the proportion of stronger hurricanes (categories 4–5) by 25% to 30% compared with weaker hurricanes (categories 1–2). With the new $14.6 billion Hurricane Storm Damage Risk Reduction System providing a 100-year storm surge–defensive wall across the Southeast Louisiana coast, New Orleans will be ready for stronger storms in the future.

Overview of statewide geophysical surveys for ecosystem restoration in Louisiana

The System Wide Assessment and Monitoring Program (SWAMP) was implemented by the Louisiana Coastal Protection and Restoration Authority (CPRA) to develop an Adaptive Management Implementation Plan (AMIP). SWAMP ensures that a comprehensive network of coastal data collection/monitoring activities is in place to support the development and implementation of Louisiana’s coastal protection and restoration program. Monitoring of physical terrain is an important parameter of SWAMP. For the first time a systematic approach was adopted to undertake a geophysical (bathymetric, side-scan sonar, sub-bottom profile, and magnetometer) survey along more than 5,000 nautical miles (nm) (excluding the 1,559 nm currently being surveyed from west of Terrebonne Bay to Sabine Lake) of track-line in almost all of the bays and lakes from Chandeleur Sound in the east to Terrebonne Bay in the west. This data collection effort complements the regional bathymetric survey undertaken under the Barrier Island Comprehensive Monitoring (BICM) Program in the adjacent offshore areas. This paper describes how a study of this magnitude was conceptualized, planned, and executed along the entire Louisiana coast. It is important to note that the initial intent was to collect bathymetric data only for numerical modelling for ecosystem restoration and storm surge prediction. Geophysical data were added for oyster identification and delineation. These first-order data also help comprehend the regional subsurface geology essential for sediment exploration to support Louisiana’s marsh and barrier island restoration projects.

Ecosystem restoration in Louisiana — a decade after the Deepwater Horizon oil spill

Louisiana has a long history of coastal management and restoration actions with multiple projects implementing common approaches. Traditionally, most of the restoration efforts have been ongoing in Louisiana by state and federal agencies through the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA). These activities are now being expanded significantly through additional funding and implementing entities such as the Resources and Ecosystems Sustainability, Tourist Opportunities, and Revived Economies of the Gulf Coast States (RESTORE) Act of 2012 Council, National Resource and Damage Assessment (NRDA) through the Louisiana Trustee Implementation Group (LA TIG), and the National Fish and Wildlife Foundation (NFWF). Considering a broader ecosystem or landscape context for implemented restoration projects can provide a framework for emphasizing commonality of restoration goals. Such a framework allows for multiple benefits of restoration efforts to be quantified, including prioritized natural resources, ultimately assessing the effectiveness of large-scale restoration efforts in coastal Louisiana. Three disasters have completely changed the trajectory of Louisiana’s coastal resto- ration and protection program. Hurricanes Katrina and Rita (2005) compelled the state to take serious note of the vagaries of nature, especially high-energy events like hurricanes, and to develop a comprehensive/robust coastal protection and restoration plan. Five years later, the Deepwater Horizon (DWH) oil spill exposed the fragility of the Louisiana coast but at the same time penalty monies provided much needed funding to implement the state’s coastal protection and restoration plans. This paper provides a high-level assessment of project implementation and makes the case that Louisiana could move quickly in the implementation of various restoration plans because robust and comprehensive restoration plans were previously developed and are available. Here, it must be appreciated that for the first time, dedicated funding is available not only for regional programmatic monitoring to implement adaptive management, but also for development of the art and science of restoration. It is also suggested that for efficient and cost effective implementation of Louisiana’s Coastal Master Plan federal agencies must work in tandem with the state/CPRA who not only bring the most comprehensive plan but expertise along with institutional knowledge to the table.

Field-based Estimate of the Sediment Deficit in Coastal Louisiana

Coastal and deltaic sediment balances are crucial for a region’s sustainability. However, such balances remain difficult to quantify accurately, particularly for large regions. We calculate organic and mineral sediment mass and volume balances using field measurements from 273 Coastwide Reference Monitoring System sites across the Louisiana coast between 2006 and 2015. The rapid relative sea level rise rate (average 13.4 mm/yr) is offset by the small dry bulk densities observed (average 0.3 g/cm3) to produce a 16.2 ± 41.1% mass deficit and 24.1 ± 14.0% volume deficit, significantly smaller than recent predictions for 2000 – 2100 (73 to 79% mass deficit). Geostatisical estimates show that this deficit is primarily located in areas not directly nourished by major rivers, yet these regions still accumulate ~24 MT/yr of mineral sediment. A fluvial sediment discharge of 113.8 MT/yr suggests a coast-wide trapping efficiency of 31.5 ± 15.8% of the riverine sediment, excluding subaqueous deposition. Organic accumulation accounts for 30% of all volume accumulation during our study period and total organic mass accumulation per unit area is relatively constant in both directly and indirectly nourished regions. Sediment characteristics in the modern coastal wetlands differ from the Holocene deposit, suggesting secular changes within the system that will likely continue to influence coastal dynamics over the coming decades. Our results suggest that the gap between accommodation and accumulation (mass or volume) during this decade was not as large as the previously predicted century average.

MODELING THE EFFECT OF LAND-BUILDING PROJECTS ON STORM SURGE AND HURRICANE WAVES IN COASTAL LOUISIANA

Wetland loss on the hurricane-prone Louisiana coast continues at an alarmingly high rate. Coastal Louisiana is at risk of losing between 2118 and 4677 km2 of land over the next 50 years (Couvillion et al., 2013). To combat the devastating wetland loss, the Louisiana 2017 Coastal Master Plan (CMP) called for sediment diversions along the lower Mississippi River to enhance sediment supplies to coastal wetlands and build more wetlands. The Louisiana Coastal Protection and Restoration Authority (CPRA) plans to spend $2 billion on the Mid-Breton and Mid-Barataria sediment diversion projects. In this study, numerical experiments were conducted to quantify the effect of land-building projects on storm surge and hurricane waves in Barataria and Breton Basins of Louisiana.

ASSESSMENT OF THE EVOLUTION OF STORM SURGE IN COASTAL LOUISIANA

The Louisiana coastal landscape comprises an intricate system of fragmented wetlands, natural ridges, man-made navigation canals, flood protection and oil and gas infrastructure. Louisiana lost approximately 1,883 square miles (4,877 sq km) of coastal wetlands from 1932 to 2010 including 300 square miles (777 sq km) lost between 2004 and 2008 due to Hurricanes Katrina, Rita, Gustav and Ike (Couvillion et al., 2011). A projected additional 2,250 square miles (5,827 sq km) of coastal wetlands will be lost over the next 50 years if no preventative actions are taken (Coastal Protection and Restoration Authority of Louisiana, 2017). Storm surge models representing historical eras of the Louisiana coastal landscape can be developed to investigate the response of hurricane storm surge (e.g. peak water levels, inundation volume and time) to land loss and vegetative changes. Land:Water (L:W) isopleths (Gagliano et al., 1970; Twilley et al., 2016; Siverd et al., 2018) have been calculated along the Louisiana coast from Sabine Lake to the Pearl River. These isopleths were utilized to develop a simplified coastal landscape (bathymetry, topography, bottom roughness) representing circa2010. Similar methods are employed with the objective of developing storm surge models that represent the coastal landscape for past eras (circa1890, c.1930, c.1970).

Evaluation of the Effectiveness of a Coastal Wave Reduction and Sediment Retention Structure Using CFD Simulations

The Louisiana coast experiences significant erosion due to wave actions. There are wetlands and marshes located in the coastal areas, however loss of these wetlands is a major threat. Although coastal waves and floods cause erosion, they do carry sediments, which can potentially counter-act some of the wetland losses. Innovative shoreline protection designs that reduce the wave actions but still allow sediments to travel through could be very beneficial. This research aims to evaluate the effectiveness of the wave reduction and sediment retention of several such designs using CFD simulations. CFD simulations were used to determine the alternations of the wave characteristics and the sediment transport with the designed structures. Small scale experiments of such designs will be conducted in a wave tank facility to validate the modeling results. The research aims to disclose the detailed physics of the flow and sediment transport in this complicated flow-structure interaction problems, and, based on the discoveries, we will provide suggestions to improve the current design to enhance the performance significantly.