Fundamentally, all my research investigates the physics of the coastal ocean and its interactions with the atmosphere or humans, applying a combination of computational modeling, statistical analysis and fixed observational stations. In the past five years, my primary tool has been modeling and the topic areas have been (1) physics of coastal storm surge, (2) probabilistic assessment of coastal floods and climate change, and (3) mitigation or adaptation to coastal hazards, which has seen vigorous interest regionally after the strong impacts of Hurricane Sandy.


Influence of wind and pressure on Hurricane Sandy’s storm surge. Winds (arrows) blowing in from the northeast across the Atlantic Ocean during the days preceding Sandy’s landfall started to pile water up against the mid-Atlantic coast. Due to Earth’s Rotation (and the “Coriolis Effect”) the net flux of water moves to the right of the wind direction. As Sandy itself approached, atmospheric pressure (black lines) gradients from high pressure areas to the the low-pressure center of the storm cause water to rise under the storm, called the “inverse barometer effect”. The animation here runs from late Oct. 26 through Sandy’s peak surge onto land at about 10 p.m. on Oct. 29, and beyond. The large image shows storm surge across the region, mapped onto longitude and latitude. The inset graph shows the surge height by the New York City shore at Sandy Hook, N.J., as does the mapped colors (scale bar at far right). Tides are not included in this simulation.

In the topic area of physics of coastal storm surge, my contributions have shed light on its dependence on wind stress, wave radiation stress, coastal morphology, and estuary stratification and freshwater inputs.  I contributed a major improvement to the Stevens Institute’s coastal flood forecasting system by incorporating the effects of storm waves on wind stress. That paper also demonstrated the importance of two estuary processes that are often neglected by other forecast systems, a widely-cited finding (Orton et al., 2012).  Another useful improvement is in progress – my recent post-doc Reza Marsooli and I studied air-sea-wave interactions by incorporating a new “rapid” wave model that includes more physical processes than other rapid wave models, including wave radiation stress and vegetation drag.  This new coupled hydrodynamic-wave model has the potential to improve probabilistic forecasts and risk assessments that require ensembles of hundreds-to-thousands of simulations, due to its rapid speed relative to more widely-used models (Marsooli et al., 2016; Marsooli et al., 2017a; Marsooli et al., 2017b).  Another area of great progress has been the study of interactions between coastal morphology, tides and storm surge.  My published work has revealed how inlet width and depth (Orton et al., 2015c), and tide resonance and sea level rise (Kemp et al., 2017; Orton et al., 2015b), all interact and influence coastal flooding.  This new process-knowledge, along with the model improvements described above, are guiding the development of novel concepts for mitigation of coastal hazards, discussed in the second and third topic areas below.



Historical and modeled TC storm tracks affecting New York Harbor (NYH), shaded by Saffir-Simpson category (Cat). (top) Known TC or hybrid TC/ETC 1.25 m or greater surge events at NY Harbor, 1788-2013, with year, name (if any), and observed storm surge. (bottom left) Select modeled TC tracks, on a map that includes the landfall gate numbers. Storms are shown that led to storm tides close to the 100-year event (2.5-2.9m) which occur at a rate higher than 0.0001 y-1. (bottom right) Storms that led to the largest storm tides in the set, from 5.2-5.7 m (Orton et al. 2016).

Probabilistic information on natural hazards is valuable for decision-makers, enabling mitigation studies and economic benefit-cost analyses that are often considered best-practices for development.  However, hurricane flood probabilities form a particularly challenging problem, defined by rare events that may not have occurred in the brief historical record.  In response to demand from New York City and other regional stakeholders, myself and a few regular collaborators have developed novel dynamic modeling and probabilistic analysis techniques for quantifying flood risk from hurricanes at the coast (Orton et al., 2016b), as well as in tidal river systems where rainfall merges with storm surge (Orton et al., 2015a). We have also extended these techniques to nonstationary analysis of evolving flood probabilities (Talke et al., 2014), included the effects of sea level rise (http://AdaptMap.infoOrton et al., 2016a; Orton et al. submitted 2017), and tested simplified flood mapping methods that alleviate the need for detailed dynamical modeling (Orton et al., 2015b).

Studies of coastal hazard mitigation by engineered “gray” infrastructure and natural or nature-mimicking features are a natural follow-on to a disaster like Hurricane Sandy.  The technical methods developed above have enabled much of my recent work in quantitative analysis of flood mitigation strategies.  Immediately in the aftermath of Sandy, we were enlisted by New York City’s Special Initiative on Rebuilding and Resilience, leading to research showing that a small shift in Sandy’s landfall timing could have led to a worse flood disaster (Georgas et al., 2014).  We contributed to New York City’s $20 billion flood mitigation plan (City of New York, 2013) and won the federal Housing and Urban Development (HUD) Rebuild By Design competition with a project called “Living Breakwaters” and generally studied how oysters or biochemically-attractive concrete can reduce coastal storm damages (Brandon et al., 2016; Orff et al., 2014).  A broad range of quantitative analysis of flood mitigation efforts has followed, including benefit-cost analysis (Orton et al., 2016a) and physical modeling of water and waves moving through wetlands (Marsooli et al., 2016; Marsooli et al., 2017b).  I proposed and modeled novel concepts for flood mitigation using sand replenishment in an estuary (http://AdaptMap.infoOrton et al., 2016a; Orton et al., 2015c), and these results have subsequently received serious consideration in city-led community-guided mitigation studies.