Effects of Beach Nourishment Project on Coastal Geomorphology and Mangrove Dynamics in Southern Louisiana, USA

Abstract

Relative sea-level (RSL) rise associated with decreased fluvial sediment discharge and increased hurricane activity have contributed to the high rate of shoreline retreat and threatened coastal ecosystems in Port Fourchon, Louisiana, USA. This study, based on QuickBird/drone images (2004–2019) and LIDAR data (1998–2013), analyzed the impacts of shoreline dynamics on mangroves (Avicennia germinans) and marshes before and after the initiation of a beach nourishment project in 2013. The coastal barrier and dune crest migrated landward between 1998 and 2013. Meanwhile, the dune crest height increased between 1998 and 2001, then decreased in 2013, probably due to hurricane impacts. The total sediment volume along this sandy coastal barrier presented an overall trend of decline in the 1998–2013 period, resulting in a wetlands loss of ~15.6 ha along 4 km of coastline. This has led to a landward sand migration onto muddy tidal flats occupied by Avicennia germinans (1.08 ha) and Spartina (14.52 ha). However, the beach nourishment project resulted in the advancement of the beach barrier from Nov/2012 to Jan/2015, followed by a relatively stable period between Jan/2015 and Mar/2019. Additionally, both the dune crest height and sediment volume increased between 2013 and 2019. This set of factors favored the establishment and expansion of mangroves (3.2 ha) and saltmarshes (25.4 ha) along the backbarrier environments after 2013, allowing the tidal flats to keep pace with the RSL rise. However, waves and currents caused shoreline erosion following the beach nourishment project between Oct/2017 and Nov/2019, threatening wetlands by resuming the long-term process of shoreline retreat.

A timely method for post-disaster assessment and coastal landscape survey using drone and satellite imagery

“…During the past 5 years, we have published a total of 12 studies using this method to monitor the mangroves and coastal sedimentary dynamics from South and North America in the light of climate change [4] , [5] , [8] , [10] , [11] , [12] , [13] , [14] , [15] , and this method has attracted interests from numerous scholars from across the globe. Thus, we believe this procedure can provide an effective way for post-disaster assessment and coastal landscape survey in a timely fashion.…”

“…To date, remote sensing is still the most common method of studying coastal landform dynamics [ 4 , 5 ]. This method is time-tested and relies on high resolution satellite imagery such as lidar and QuickBird.…”

Impacts of Coastal Infrastructure on Shoreline Response to Major Hurricanes in Southwest Louisiana

“…The breakwaters are part of a shoreline stabilization effort that has been discussed since at least 2001 (Hill and Belhadjali, 2005). The system was a collaboration between the National Oceanographic and Atmospheric Association (NOAA), the Louisiana Coastal Protection and Restoration Authority (CPRA), Louisiana Department of Wildlife and Fisheries (LDWF), and the National Marine Fisheries Service, with $34 million of funding secured from the Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) to construct a 6.4 km transect of emergent breakwaters along the RWR shoreline designed for Category 1 conditions (Jafari et al, 2020;Cohen et al, 2021;Reid, 2021). Funded as "ME-18," the multi-million-dollar project incorporated a Light Weight Aggregate Concrete (LWAC) breakwater system.…”

Evaluating the Impact of Engineering Works in Tidal Flats Using Time-Series Satellite Images – Case of the Mont-Saint-Michel Bay, France

“…In China, the extension of the port facilities disrupts sedimentation along the Yellow Sea coast [3]. A beach nourishment project in Louisiana (USA) had impacts on the dynamics of the shoreline made of mangroves and marshes [4]. In the Po River estuary, which is not a tide-dominated delta, the importance of episodic events such as heavy floods has been highlighted [5].…”