Natural and Nature-Based Features for Coastal Resilience: Designing Field-Based Experiments for Measuring Hurricane Storm Surge and Wave Attenuation by Marshes

Abstract

In the course of extreme weather, coastal communities suffer significant risk of damage due to impact from waves and storm surges. In North Carolina, the Outer Banks, a popular tourist destination due to its numerous beaches and waterfronts, is among one of the many locations in danger. For instance, Hurricane Dorian devastated the barrier islands of North Carolina causing up to $50 million in damages. To help mitigate these hazards, natural and nature-based features (NNBF) have been acclaimed as a possible solution to alleviate these coastal hazards. However, our understanding on the potential of NNBF functions is still limited, making it challenging to compare their benefits to more traditional coastal resilience approaches (i.e. seawalls, breakwaters, revetments). Therefore, documenting the potential of these ecosystems to reduce wave energy based on field-scale experiments is crucial to enable its full adoption as a reliable coastal defense. To obtain accurate data, we established precise locations for hydrodynamic and waves sensors based on numerical modeling of past hurricanes and an evaluation of their impact. When examining the modeling results, as the water reaches the vegetation, it is prevalent to find an exponential wave decay to identify the best sensor placements to capture the effects in the research area. The study site is located in Frisco, NC, where the sensors intended to be used include the Hobo Onset U201 (low-frequency pressure transducer to measure water levels), and the RBR D|wave16 (high-frequency pressure sensor to measure wave heights). We simulated Hurricane Irene (2011) with the numerical model XBeach to estimate the potential impacts that hurricanes have on marshes in the Outer Banks. Through these simulations we looked at the effectiveness of the marshes at reducing the wave heights to understand the possible protection marshes may provide, by comparing vegetation and synthetic non-vegetation scenarios. The placement of the sensors was determined after the analysis of the wave attenuation curves during time varying water levels and wave heights for both scenarios, based on the wave height that was influenced by vegetation. With reliable placements of these sensors, further data will be capable of illustrating the impact NNBF has on wave attenuation, supporting further academic analysis of NNBF potential to protect coastal communities and infrastructure.