Local Conentration of Waves due to Abrupt Alongshore Variation of Nearshore Bathymetry

Small-scale physical and numerical experiments were conducted to investigate the local concentration of waves (monochromatic and group) due to abrupt change of nearshore bathymetry in alongshore direction. Wave run-up motions along the shoreline were measured using an image analysis technique to compare localized concentration of wave energy, when waves propagate a over bathymetry composing rhythmic patterns of mild/steep slope bottom configurations. Measured alongshore variation of maximum wave run-up heights showed significant peak near the boundary, which has sudden alongshore change of depth, both under monochromatic and group wave trains. This phenomenon is found to be due to interaction of waves with neashore currents, which is further enhanced by excitation of long wave components by breaking of group waves. Furthermore, this paper discusses results of preliminary experiments carried out to test the effectiveness of several shore protection structure layouts in mitigating such wave concentrations. Numerical simulations were performed by using a model developed based on Nwogu (1993) Boussinesq-type equations; coupled with a transport equation to model energy dissipation due to wave breaking.

Autonomous bathymetry for risk assessment with ROAZ robotic surface vehicle

The use of unmanned marine robotic vehicles in bathymetric surveys is discussed. This paper presents recent results in autonomous bathymetric missions with the ROAZ autonomous surface vehicle. In particular, robotic surface vehicles such as ROAZ provide an efficient tool in risk assessment for shallow water environments and water land interface zones as the near surf zone in marine coast. ROAZ is an ocean capable catamaran for distinct oceanographic missions, and with the goal to fill the gap were other hydrographic surveys vehicles/systems are not compiled to operate, like very shallow water rivers and marine coastline surf zones. Therefore, the use of robotic systems for risk assessment is validated through several missions performed either in river scenario (in a very shallow water conditions) and in marine coastlines.

Bathymetry of Lake Constance - State-of-the-art in surveying a large lake

In 2014 the by far largest German lake has been newly surveyed. The transnational project is funded by the European Union and delivers a detailed 3D-model of the lake- floor. The German project name is »Tiefenschärfe – Hochauflösende Vermessung Bo- densee«, which in English roughly means: high-resolution survey of Lake Constance. The German term »Tiefenschärfe« (in optics and photography: depth of field) plays with the meanings of »Tiefe« (depth) and »Schärfe« (sharpness). The result of the sur- vey shall be a clear and sharp image of the deep and shallow lake- floor. At present the LiDAR and multibeam data are still processed, but first results are presented in this article.

Bathymetry of Lake Constance – a High-Resolution Survey in a Large, Deep Lake

Within the project “Tiefenschärfe – hochauflösende Vermes- sung Bodensee” a high-resolution seamless terrain model is created using airborne topobathymetric laserscanning and multibeam echosounder (MBES) techniques. The project visu- alizes the enormous wealth of features of underwater land- scapes of lakes. The combination of hydroacoustic (multibeam echosounder) and laser-optic (topobathymetric laserscan- ning) methods was used for the first time in a freshwater body of this size. Opportunities, limitations and restrictions of these high-resolution methods are presented.