Breakwater Gaps & Wave Diffraction: Where & Why they exist

Breakwaters are coastal structures that are built for the simple purpose of reducing the wave energy that reaches the coast. They can be arranged in different configurations to offer different benefits. One common application of breakwaters is to create harbors, where breakwaters are arranged to create an enclosed area of water adjacent to the coast. Harbors provide a safe location where boats can be moored while being protected from the harsh conditions of the open water. The barriers block waves and minimize the wave energy inside. Harbors, however, cannot be entirely closed from the open water. They also require gaps open to the neighboring body of water. These gaps are important to harbors primarily to allow boats to travel in and out, but also to allow fresh water to circulate through the harbor. Unfortunately, there is also an inherent problem that exists with these necessary gaps: waves enter the harbor in these segments and diffract through the harbor, distributing wave energy.

Portland Harbor, Oregon

Nick Dosch
Professor Chin Wu
Civil Engineering 514
University of Wisconsin-Madison
Copyright 2010