Accidental breaches do not happen often. But when they do, hydraulic engineers must know what to do, and react fast and smartly. This practical course will teach you to prepare a safe and solid plan to get a gap closed, both in case of emergency as well as in case of a pre-planned operation.
Closing a gap in a breached dike or closing a tidal inlet seems simple in first instance but, in fact, many closure works fail just before completion. During the closing process the velocities in the gap increase considerably, leading to unforeseen complications. This has happened for example with a number of emergency closures in the Yangtze River in 1998, and along the Oder in Germany in 2002. But also the planned closure of the Miele estuary in Germany was complicated by exactly this problem.
In case of emergency closures, action is often taken based on panic. Very often these actions aggravate the situation, instead of resolving it. For planned closures of inlets the time pressure (and panic) by virtue is less, but as these works are often bigger and more comprehensive, mistakes can have a huge impact and lead to risky situations.
Hydraulic engineers confronted with closure works (either planned or in case of emergency) have to understand the hydraulic processes occurring during a closure. And they have to know what kind of actions should be undertaken given the hydraulic conditions of that moment. In most cases public opinion stresses to put “things” in the closures gap but this usually worsens the situation; velocities increase in an uncontrolled way. Before starting the final closures one should define the best location (usually somewhat inside the gap, because there velocities are lower and depth is less) and protect the bed at that location to prevent uncontrolled scour in the final phase. With relatively simple tools this can be done. In this course, we will present and discuss these tools and provide a number of exercises to train their use.