Abstract
Anthropogenic activities and climate change in coastal areas require continuous monitoring for a better understanding of environmental evolution and for the implementation of protection strategies. Surface moisture is one of the important drivers of coastal variability because it highly affects shoreward sand transport via aeolian processes. Several methods have been explored for measuring surface moisture at different spatiotemporal resolutions, and in recent years, light detection and ranging (LiDAR) technology has been investigated as a remote sensing tool for high-spatiotemporal-resolution moisture detection. The aim of the present study is the assessment of the performance of a permanent terrestrial laser scanner (TLS) with an original setting located on a high position and hourly scanning of a wide beach area stretching from a swash zone to the base of a dune in order to evaluate the soil moisture at a high spatiotemporal resolution. The reflectance of a Riegl-VZ2000 located in Noordwijk on the Dutch coast was used to assess a new calibration curve that allows the estimation of soil moisture. Three days of surveys were conducted to collect ground-truth soil moisture measurements with a time-domain reflectometry (TDR) sensor at 4 cm depth. Each in situ measurement was matched with the closest reflectance measurement provided by the TLS; the data were interpolated using a non-linear least squares method. A calibration curve that allowed the estimation of the soil moisture in the range of 0–30% was assessed; it presented a root-mean-square error (RMSE) of 4.3% and a coefficient of determination (R-square) of 0.86. As an innovative aspect, the calibration curve was tested under different circumstances, including weather conditions and tidal levels. Moreover, the TDR data collected during an independent survey were used to validate the assessed curve. The results show that the permanent TLS is a highly suitable technique for accurately evaluating the surface moisture variations on a wide sandy beach area with a high spatiotemporal resolution.
Highlights
Anthropogenic activities and climate change are an increasing risk factor for coastal environments, as they cause ecological and socioeconomic damage
A calibration curve was obtained by comparing in situ moisture data with the reflectance data measured by the terrestrial laser scanner (TLS)
Where k = −k1 /k3, b is the reflectance measured by TLS (in), wmax represents the saturation values assumed for moisture content wmin, Ec,min are the minimum detectable probe values for w, and k1, k2, and k3 are constants to be determined
Summary
Anthropogenic activities and climate change are an increasing risk factor for coastal environments, as they cause ecological and socioeconomic damage. The influences of weather conditions, changing tides, waves, river outflow, and human construction on sandy coasts have triggered the need for continuous monitoring of coastal areas. This will lead to a better understanding of the environmental processes and will enable the evaluation of coastal protection projects. Coastal dunes form the main line of defense against the sea on sandy coasts. Their evolution depends on sediment supply, beach morphology, vegetation, and climatic variables [1]. Their evolution depends on sediment supply, beach morphology, vegetation, and climatic variables [1]. 4.0/).
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