In chapter 5 it was indicated that in the case of the closure of a river branch or an estuary, it is very important to know the velocities in the closure gap. This is because velocities in the gaps determine the stability of the material used and the choice of the closing strategy. There are fundamentally two ways to determine the velocities in the gap, both of which are used at different stages in the design process and depending on circumstances.

At an early stage, it can be very useful to get a rough idea of the situation by making a simple manual computation using the theory of Chezy. At a more definitive stage or in a more complex situation a mathematical model is often used. The simplest model is a 1-D model like Duflow.

For this lecture you need to read Breakwaters and Closure Dams, Chapter 16