Advancing the Understanding of Storm Processes and Impacts by Nicole Elko, Casey Dietrich, Mary Cialone, Hilary Stockdon, Matt W
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Hurricanes Katia, Irma, and Jose from west to east on 8 September 2017 (Photo credit: NASA/NOAA GOES Project). U.S. Coastal Research Program Advancing the understanding of storm processes and impacts By Nicole Elko, Casey Dietrich, Mary Cialone, Hilary Stockdon, Matt W. Bilskie, Brandon Boyd, Bianca Charbonneau, Dan Cox, Kendra Dresback, Steve Elgar, Amanda Lewis, Patrick Limber, Joe Long, Chris Massey, Talea Mayo, Kathryn McIntosh, Norberto Nadal-Caraballo, Britt Raubenheimer, Tori Tomiczek, and Anna Wargula n 2017, Hurricanes Harvey, Irma, and To determine needed advancements eXperiment), anticipated in 2020-2021, Maria caused more than $200 billion in storm forecasting, the U.S. Coastal were presented to encourage continued dollars of damage in the United States, Research Program (USCRP) hosted a engagement of coastal researchers across Ias well as the incalculable cost of the loss Storm Processes and Impacts workshop disciplines. of life and mental trauma associated for coastal stakeholders 16-18 April This paper represents a synthesis of the with these disasters (Sullivan 2017). In 2018, in St. Petersburg, Florida. The at- forecasting challenges, research needs, a changing climate, sea level rise and the tendees included local coastal managers, infrastructure improvements, and com- potential for increasing tropical cyclone emergency managers, state and regional munication challenges presented and intensity can result in even more devastat- agencies, federal agency scientists and discussed during the workshop. Each ing damages (IPCC 2013; Knutson et al. engineers, academics, and private indus- section includes a table of prioritized 2010). Therefore, engineers, community try scientists and engineers. Workshop challenges or needs based on the work- planners, and coastal residents need ac- objectives were to synthesize present shop participants’ feedback. curate, timely, and accessible forecasting capabilities for modeling storm processes of storm processes and their impact on and forecasting impacts and to prioritize Three main research goals to address coastal communities to bolster national advancements. In addition, the workshop forecasting challenges and advance storm resilience and reduce risk to life and provided an opportunity to bridge the ap- impact predictions were identified: (1) property during these events. However, parent gap between the research of coastal expand the understanding and repre- along with uncertainties in understand- scientists and engineers and the infor- sentation of dynamic feedbacks between ing and modeling of storm processes, mation being distributed publicly and multiple time/length scales and processes there are complex challenges associated to emergency managers before, during, (Represent Dynamic Feedbacks); (2) with determining and meeting the needs and after storm events. Finally, plans for improve forecasting methodology and of end users who rely on these forecasts a large-scale, extreme-event field experi- communicate inherent model uncer- for emergency management decisions. ment, DUNEX (During Nearshore Event tainty (Improve Forecasting Methods); Shore & Beach Vol. 87, No. 1 Winter 2019 Page 37 Table 1. about the timing of evacuation orders Prioritized forecasting challenges (Table 2). 1 — Integrate multiple hazards/processes over temporal & spatial scales The specific research needs (Table 2) 2 — Valuate accuracy of meteorological conditions were grouped into the following research 3 — Determine & propagate uncertainty themes or goals which are discussed in 4 — Predict timeline and level of impact the sections below. n Represent the dynamic feedbacks and (3) quantify the role of nature-based Furthermore, forecasting the impacts among storm-driven hydro- and mor- and engineered shorelines in mitigating of these hazards requires accurate me- phodynamics (2, 3, 4, 9); storm effects (Assess Hazard Mitigation). teorological conditions that may not be To advance these goals, improvements available. Storm track errors increase 30- n Improve forecasting methods to in observations and modeling (Infra- 40 nautical miles per day prior to landfall, better account for uncertainties (1, 5, 7, structure) are needed. A final challenge and errors in intensity forecasts increase 12); and involves translating these processes, for three days, then level off (hurricanes. n forecasts, and uncertainties to the end gov/surge). Determining and propagating Assess the hazard mitigation capa- user (Communication). this uncertainty into storm models and bilities of natural, nature-based, and built then into forecasts poses a significant features (6, 8, 10, 11). FORECASTING CHALLENGES challenge, and thus it is difficult to predict Forecasting challenges prioritized by REPRESENT the timeline and impact levels on the workshop participants are given in Table DYNAMIC FEEDBACKS temporal scales required by emergency 1 and discussed below. Workshop participants identified managers who are often expected to begin research needs related to the dynamic Extreme storms involve multiple making decisions up to one week before feedback between physical (hydrody- hazards driven by a variety of coastal storm impact. namic) processes and the system (mor- processes that operate on different tem- Forecasting at adequate spatial reso- phologic) response during storm events. poral and spatial scales. Storm surge, lution also presents a challenge. There Four specific objectives identified were to: dangerous surf, strong and damaging is a discrepancy in the resolution of 1) better understand sediment transport winds, tornadoes, and extreme rainfall national-scale models like the Sea, Lake, to improve our ability to simulate mor- can all contribute to the overall storm and Overland Surges from Hurricanes phologic change, 2) integrate relevant hazard. However, each of these hazards (SLOSH) model, which have a typical grid physics into numerical models, couple the may impact a coastal community at a dif- cell resolution of 500 to 1,000 m in coastal models, and provide a feedback mecha- ferent time during a storm, and the state regions, as compared to the parcel- to nism between models, 3) include the ef- of the art of mapping and modeling these street-level resolution required for evacu- fects of vegetation and sedimentation on multiple hazards has not yet advanced to ation zone assignments (Kerr et al. 2013). beach and dune response and recovery, provide coupled forecasts about water- and 4) incorporate rainfall runoff into related hazards. Emergency managers RESEARCH NEEDS the hydrodynamic and morphodynamic may be utilizing discrete products to Workshop participants prioritized a modeling capabilities. To represent assess the impacts of large rainfall events number of specific research needs, rang- these dynamic feedbacks during storms, and storm surge impacts. The integration ing from fundamental science questions research will require the integration of of multiple hazards and processes over (e.g. better understanding sediment multiple processes over a range of spatial the course of an extreme event remains a transport to improve morphologic and temporal scales as discussed in the significant forecasting challenge. change models) to practical questions forecasting challenges section above. Table 2. The coupling between hydrodynam- Prioritized research challenges ics and morphodynamics on a variety of spatial and temporal scales is needed 1 — Quantify spatial/temporal resolution and accuracy required for users to understand and predict the full range 2 — Improve models to integrate relevant processes of coastal impacts from storms and the 3 — Expand understanding of sediment transport – model improvements in recovery of beaches that occurs between morphology individual storms events. For instance, 4 — Determine feedbacks between physical processes feedbacks (two-way coupling) between 5 — Determine inputs for accurate coastal hazard forecasts in probabilistic ocean waves, wave-driven currents, and models geomorphology may result in offshore 6 — Study mitigation solutions - how to mitigate hazards movement of sandbars during storms 7 — Learn from model error to improve process understanding and models (Thornton and Humiston 1996, Gallagher 8 — Quantify the value of nature and nature-based features et al. 1998) and onshore migration of 9 — Investigate beach and dune recovery the bar during small to moderate wave 10 — Understand variability of impacts depending on shoreline type – cliff, conditions (Hoefel and Elgar 2003). marsh, mangrove, ice Similar coupling between oceanographic 11 — Assess impacts to structures (hydro, load, energy, surge) and geomorphologic processes affect the 12 — Assess available statistical methods to best use limited model results movement of other features in the beach profile such as the shoreline, berm, and Page 38 Shore & Beach Vol. 87, No. 1 Winter 2019 dune. Alongshore variations in sandbar suggesting that the transport of sediment likely are important during extreme depth and location can affect the maxi- from the dune is not linearly related to events when dune and bluff erosion can mum elevation of ocean water levels and the maximum water level elevations dur- be severe and strong rip currents (and breaking wave heights and accompanying ing a storm (Long et al. 2014). Instead, undertow) may carry sediments into deep wave runup on the beach (Raubenheimer process-based models are necessary to water. The net gain or loss of material to et al. 2001, Cohn and Ruggiero 2016), account for the timing,