Covering space scales from less than a metre to several kilometres and time scales from seconds up to years, a wide range of coastal issues can be addressed, such as shoreline evolution, groins and beach nourishments. As data collection is automatically performed by unmanned video stations, operation is cost-efficient, enabling the technique to be competitive to the traditional survey methods of beach bathymetry and shoreline. Complementary to Deltares ' modelling tools like the Delft-3D system, the ARGUS video technique has been embedded as a monitoring tool in our consultancy practice.

Every daytime hour, snapshot images are collected and averaged over a period of 10 minutes, yielding time-exposure images. With the help of sophisticated routines, these oblique images can be projected on the ground plane, resulting in rectified images. These rectified images allow for the quantitative interpretation of image features. If multiple oblique images are rectified simultaneously, so-called merged images can be obtained, which give a plan view of the nearshore zone. The following figure shows an example of such a merged image of Noordwijk, The Netherlands.

Merged image (panoramic and rectified view) of Noordwijk. Five individual time-exposure images are used to compose these merged images. In the rectified image (lower panel), the shoreline is located at the lower side, around x = 0 m. The bright band of 3000 m length at about 900 m off-shore indicates the location of a 1.25 Mm³ shoreface nourishment.

The rectified video images show bright, longshore bands, clearly indicating the locations where waves preferably break. As the breaking of waves is caused by depth-limitation, the bright intensity patterns reflect underlying bottom topography. In addition, the location of the waterline can easily be identified. Taking into account the tidal level, this enables the intertidal beach bathymetry to be mapped using a sequence of hourly-sampled images. Finally, in the absence of breaking waves, local water depth could be estimated from the propagation speed of individual waves as observed from time series of image intensity at distinct locations. In this way, the morphologic changes of a coastal system can be monitored cost-effectively over long-term periods.

In practice, the ARGUS based monitoring system can be applied in the field of coastal zone management and coastal engineering, in a number of ways:

Time stack image at St. Petersburg, Florida (USA). A time stack image is obtained by sampling image intensities along a fixed cross-shore array (left hand panel) and stacking them over time (right hand panel). The positive X-axis is pointing seaward. With the help of this time stack image, the behaviour of the shoreline (indiated by green crosses) can be monitored, showing periods of considerable erosion during winter when waves are high, that alternate with a period of hardly any changes during summer.

An ARGUS based monitoring system allows for enhanced opportunities for the monitoring of coastal systems, to serve consultancy over a wide range of coastal zone management related issues. Based on data from ten ARGUS stations worldwide (see the Oregon State University site), an extensive research group is continuously working on the development of tools for the quantitative interpretation of video data. Deltares has a license agreement with Oregon State University for the installation of ARGUS stations world-wide outside Northern America. Recently, the number of sites has been extended with two more ARGUS stations, one at Egmond, The Netherlands and one at the Gold Coast, Australia.