Urban Headwater Stream Design

As watersheds develop into urban and suburban areas, the impacts and changes that occur to headwater streams are tremendous. All of the characteristics of the watershed change, seemingly, overnight. Rather than the slow change that normally occurs in nature, the changes that occur for the headwater streams of the watershed occur very rapidly. The change can be as dramatic as the creation of a stream where only small swale had previously existed. The resulting impact to adjacent property and infrastructure can be catastrophic. With this understanding, it is important to plan and design for the changes that will invariably occur for the headwater streams. This planning and design in is always challenging for designers. Physical constraints such as rights-of-way and existing or proposed infrastructure, in addition to the constraints placed on the design by economic, cultural, and political issues, often narrowly define the line between success and failure of the stream design. A review of current articles and publications quickly shows that there are many varied approaches to stream design. The results of these approaches are also just as varied. This wide range of approaches and results often leave public works agencies with more questions than answers, and results in low confidence in the design. In order to provide designs that are consistently successful and provide a high level of confidence with regulating agencies, a design procedure was developed that utilizes the techniques and approaches that have been published by some of today's leading authorities in stream mechanics. This procedure integrates fluvial geomorphology with sound hydraulic and sediment transport principles. The procedure incorporates approaches from Rosgen, Chang, Soar and Thorne, as well as agency publications from the U.S. Highway Administration, U.S. Army Corps of Engineers (USACE), and others.