Shallow-water environments

Shallow-water environments are even more essential to our everyday life than continental margins (Chapter 7). These environments directly shape and are shaped by our commercial, ecological, and leisure activities. Most of the world’s fishing is still drawn from coastal waters, particularly in developing countries, and the pressure on these resources has clearly reached the point of non-sustainable return. As fish stocks dwindle across the world, the pressure on shallow-water environments is amplified by the construction of infrastructure (harbors, dikes, coastal defenses, etc.). Modification of sediment redistribution along shores can now be clearly attributed to specific projects (e.g., along the southern British coastline, where some beaches are more eroded after others have been protected from accelerating erosion). In the past, this had led to the silting of estuaries, or the abandonment or modification of once prospering harbors (e.g., Brugge in Belgium, or antique Greek harbors now lying 5 kilometers inland). The effective monitoring and sustainable management of shallow-water environments and their habitats relies heavily on the mapping of the seabed and water column, and sidescan sonar is the tool of choice, because of its relative cost and higher ease of deployment as well as because of the customer base it has developed among many types of end-users.