Closure works

Closure dams are constructed for a variety of very different purposes; such as the
creation of a separate tidal basin for power generation or as sea defence structures
to increase safety. Compared to closure works, few other engineering works have
such an extensive impact on the environment in all aspects. For instance, the main
purpose of the construction of the Afsluitdijk closure dam in the Netherlands was
to provide protection against high storm surge levels and to facilitate land reclamation.
Additional advantages were fresh water conservation and a road connection
between the provinces of Holland and Friesland. The purpose of a closure
dam may be one or more of such objectives, but these are automatically
accompanied by other side effects, some of which may be negative. A thorough
study of these impacts is part of the design process.
 This book focuses on the technical aspects of the construction of a closure dam in
a variety of circumstances. Every closure operation is a struggle against nature.
Every action taken to obstruct the water flow will immediately be counteracted by
nature itself. The knowledge gained from experience, whether successful or not,
is supplemented by the results of advanced research and experiment. Nevertheless,
the changes in conditions during the progression of the closure are sometimes difficult to predict. Allowing for flexibility in operations that are
incorporated in the design provides an important tool.