Uncertainties in Stream Restoration for Highway Design and Improvement

Highway design and construction often requires relocation and reconstruction of stream channels. Stream restoration practices are commonly used in the relocation design to promote channel stability. Stability of a channel is a function of the channel's ability to transport its water and sediment loads. Although water discharge is considered in channel design, sediment loads are often overlooked. In order to design stable channels with sufficient sediment carrying capacity, sediment transport needs to be incorporated into the design methodology. In this paper, uncertainties in sediment transport capacity were considered in determining an overall uncertainty for the channel slope. A case study site was based on a stream channel relocation project site in central Pennsylvania, where the channel had been relocated to accommodate a new highway. Based on the study, recommendations were made regarding the use of sediment transport capacity for stream restoration.