Controlling debris at Bridges

Woody debris from upstream areas of wooded watersheds is often transported to streams during heavy rainfall events. If this debris accumulates on bridge piers, the result can be increased erosion around the bridge foundations, flooding, and loading on the bridge structure. There are a variety of structural and nonstructural methods that are available for use in managing debris at existing bridges. However, the effectiveness of these measures has been limited, and their use is fraught with uncertainty. Application and design of debris countermeasures is largely based on engineering judgment and experience. Thus, as part of a larger restoration or stream management program, knowledge and guidance regarding which methods are applicable and cost effective under a range of bridge and stream conditions, uncertainty, and functionality of the countermeasures are needed. Given the uncertainty and lack of success in managing debris accumulation at bridges and the potentially significant impacts on bridge safety, controlling debris production and transport upstream of the bridge through stream and watershed restoration may be an important management alternative.