Does vegetation accelerate coastal dune erosion during extreme events?

A broadly accepted paradigm is that vegetation reduces coastal dune erosion. However, we show that during an extreme storm event, vegetation surprisingly accelerates erosion. In 104-m-long beach-dune profile experiments conducted within a flume, we discovered that while vegetation initially creates a physical barrier to wave energy, it also (i) decreases wave run-up, which creates discontinuities in erosion and accretion patterns across the dune slope, (ii) increases water penetration into the sediment bed, which induces its fluidization and destabilization, and (iii) reflects wave energy, accelerating scarp formation. Once a discontinuous scarp forms, the erosion accelerates further. These findings fundamentally alter the current understanding of how natural and vegetated features may provide protection during extreme events.

Delaware coast Delaware surf zone injury demographics.

INTRODUCTION: Beaches are a popular destination for recreation activities. Surf zone injuries (SZI) can occur resulting from a variety of in-water activities. Little is known regarding the sustained injury types, or demographics of injured persons and activities leading to injuries. METHODS: This study examines the distribution of SZI types, activities and populations occurring on Delaware Beaches as recorded by a local level III trauma center (Department of Emergency Medicine at Beebe Healthcare in Lewes, Delaware). RESULTS: There were 2021 injuries over the eight study years (2010-2017). The relative demographics of the injured population are similar despite fluctuating injury totals (mean [SD], 253.1 [104.4]). Non-locals (n=1757) were 6.7 times more likely to be injured as their local (n=264) counterparts (RR, 2.62; 95% CI, 2.08-3.31). Males (n=1258) were 1.7 times more likely to be injured than their female (n=763) counterparts (RR, 1.29; 95% CI, 1.21-1.37). Serious injuries, defined as patients requiring admission to a trauma service, represented 9.1% (n=184) of injuries. Fatal SZI (n=6) were categorized as serious injuries. Wading (50.1%) was found to be the dominant activity associated with injury followed by body surfing (18.4%), and body boarding (13.3%). CONCLUSION: To the authors' knowledge, this study is one of the first to investigate long-term trends in SZI data, injury activity, and demographics. Better understanding of the characteristics of injuries will allow for improved awareness techniques, targeted at populations with higher injury rates.