Content uploaded by Arnaud Hequette
Author content
All content in this area was uploaded by Arnaud Hequette on May 21, 2014
Content may be subject to copyright.
Determination of sediment budget and assessment of areas at risk from coastal hazards
on the shore of northern France using airborne LiDAR
A.Crapoulet1, A.Héquette1 and A. Gardel1
1Laboratoire d’Océanologie et de Géosciences, UMR CNRS 8187 LOG, Université du
Littoral Côte d’Opale
Station Marine – 28, avenue Foch, BP 80 – 62930 Wimereux France
Adrien.Crapoulet@univ-littoral.fr, Arnaud.Hequette@univ-littoral.fr,
Antoine.Gardel@univ-littoral.fr
Despite strong urbanization and development of major harbors during the 20th century, the
coast of northern France still largely consists of coastal dunes of variable width associated
with 500 to 800 m wide, gently sloping, macrotidal sand beaches characterized by series of
shore-parallel intertidal bars. These coastal accumulation landforms, which often represent the
only barrier protecting low elevation backshore areas from marine flooding, are particularly
vulnerable to coastal hazards that may increase during the next decades due to sea level rise
associated with climate change. Climate change may have dramatic impacts along the low
unconsolidated coastlines of northern France, especially where sediment supply is limited,
which may result in negative sediment budget and recurring coastal erosion. Although several
studies have shown that the stability of the shoreline strongly depends on the local sediment
budget, no studies have been conducted so far to evaluate the changes in the coastal sediment
stock at the scale of the northern France region during recent years. The main objectives of
this study are to determine shoreline changes and variations in sediment budget at the regional
scale, to assess the role of changes in sediment volume on the stability of the shoreline, and to
indentify the areas that are the most vulnerable to coastal hazards in the near future.
This work is largely based on the acquisition and analysis of high-resolution topographic data
of the entire littoral zone of northern France using a LiDAR (Light Detection and Ranging)
airborne laser system for high precision (vertical error margin <± 15 cm), which gives a fine
rendition of the topography over large areas. LiDAR complete coverage of the coastal fringe
of the northern France was conducted in 2008-2009 and another full LiDAR survey of the
coastal zone was completed in March 2011. Additional LiDAR data have also been obtained
in September 2011 at two specific sites (East Dunkirk and Wissant Bay) where detailed in situ
topographic measurements are regularly carried out. These spatially dense elevation data sets
were used for determining topographic variations between 2008 and 2011 and for carrying out
high-resolution 3D mapping of the coastal zone. The analysis of these evolutions allowed us
to quantify sediment volume changes in coastal dunes and intertidal areas, including estuaries
that represent major sediment sinks in the coastal zone of the region. This work was
complemented by an analysis of storm surge frequency based on theoretical tidal elevations
and tide gauge data recorded at the harbors of Dunkirk, Calais and Boulogne-sur-Mer during
the last decades. Analysis of these time series of water levels enabled to estimate the return
periods of high water levels. The combination of digital elevation data with these water level
statistics allowed us to determine potentially sensitive areas that may be exposed to marine
flooding, but also to other natural hazards such as coastal erosion.
