With high anthropogenic pressure and the effects of climate change (e.g., sea level rise) on coastal regions, there is a greater need for accurate and up-to-date information about the topography of these systems. Reliable topography and bathymetry information are fundamental parameters for modelling the morpho-hydrodynamics of coastal areas, for flood forecasting, and for coastal management. Traditional methods such as ground, ship-borne, and airborne surveys suffer from limited spatial coverage and temporal sampling due to logistical constraints and high costs which limit their ability to provide the needed information. The recent advancements of spaceborne remote sensing techniques, along with their ability to acquire data over large spatial areas and to provide high frequency temporal monitoring, has made them very attractive for topography and bathymetry mapping. In this review, we present an overview of the current state of spaceborne-based remote sensing techniques used to estimate the topography and bathymetry of beaches, intertidal, and nearshore areas. We also provide some insights about the potential of these techniques when using data provided by new and future satellite missions.

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International audienceKnowing bathymetry at intermediate depth, over large areas, and at a reasonable cost is a key issue. Spaceborne remote sensing techniques must play an essential role in retrieving such bathymetry. In this paper, a method is proposed that aims to address this issue without any in situ measurements by exploiting the characteristics of the SPOT-5 satellite dataset. The proposed method is designed to provide bathymetry from two optical SPOT-5 satellite images separated by a time lag DT of 2.04 s. It relies on the estimation of several clouds of wave celerity and wavelength pairs using wavelet and cross-correlation techniques and on the linear wave dispersion relation. This method has been applied to two SPOT-5 images on a test site characterized by complex bathymetry (Saint-Pierre, La Réunion Island). A comparison of the retrieved bathymetry with in situ bathymetric measurements reveals good morphological agreement. The mean relative error is less than 30% in the 3–80-m water depth range. The methodological choices made during method development are discussed based on additional computations, and guidelines for using the proposed method on other images at other sites are provided

Abstract. In this paper, we present new results on the potential La Palma collapse event, previously described and studied in Abadie et al. (2012). Three scenarios (i.e., slide volumes of 20, 40 and 80 km3) are considered, modeling the initiation of the slide to the water generation using THETIS, a 3D Navier–Stokes model. The slide is a Newtonian fluid whose viscosity is adjusted to approximate a granular behavior. After 5 min of propagation with THETIS, the generated water wave is transferred into FUNWAVE-TVD (Total Variation Diminishing version of FUNWAVE) to build a wave source suitable for propagation models. The results obtained for all the volumes after 15 min of Boussinesq model simulation are made available through a public repository. The signal is then propagated with two different Boussinesq models: FUNWAVE-TVD and Calypso. An overall good agreement is found between the two models, which secures the validity of the results. Finally, a detailed impact study is carried out on La Guadeloupe using a refined shallow water model, SCHISM, initiated with the FUNWAVE-TVD solution in the nearshore area. Although the slide modeling approach applied in this study seemingly leads to smaller waves compared to former works, the wave impact is still very significant for the maximum slide volume considered on surrounding islands and coasts, as well as on the most exposed remote coasts such as Guadeloupe. In Europe, the wave impact is significant (for specific areas in Spain and Portugal) to moderate (Atlantic French coast).

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Within an effort to estimate near-shore bathymetry from satellite scenes, a method based on wave celerity and wavelength estimation is developed. These wave characteristics are extracted from SPOT-5 panchromatic and multispectral scenes. The method allows us to associate the wavelength and the celerity of the same detected wave and to estimate the water depth from the dispersion relation. This technique is tested on Saint Pierre area (La Reunion Island). Results are compared to in-situ measurements and show a reasonable agreement in terms of morphology and a mean absolute bathymetric error inferior to 30 % in intermediate depths (5-30 m range).

Abstract. The devastating Mw 7.1 Haiti earthquake in 2010 was accompanied by local tsunamis that caused fatalities and damage to coastal infrastructure. Some were triggered by slope failures of river deltas in the close vicinity of the epicenter, while others, 30 to 50 km to the north across the Bay of Gonâve, are well explained by the reverse component of coseismic ground motion that accompanied this mostly strike-slip event. However, observations of run-up heights up to 2 m along the southern coast of the island at distances up to 100 km from the epicenter, as well as tide gauge and DART buoy records at distances up to 600 km from the epicenter, have not yet received an explanation. Here we demonstrate that these observations require a secondary source, most likely a submarine landslide. We identify a landslide scar 30 km from the epicenter off the southern coast of Haiti at a depth of 3500 m, where ground acceleration would have been sufficient to trigger slope failure in soft sediments. This candidate source, 2 km3 in volume, matches observations remarkably well assuming that the sediment collapse obeys a viscous flow with an initial apparent viscosity of 2×105 Pa s. Although that particular source cannot be proven to have been activated in 2010, our results add to a line of evidence that earthquake-triggered submarine landslides can cause significant tsunamis in areas of strike-slip tectonic regime.

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