Risk Assessment for Stream Modification Projects in Urban Settings

The dynamic and stochastic nature of riverine ecosystems creates considerable uncertainty within the practice of stream modification. For streams in urban environments, this uncertainty results in risk to the environment and infrastructure. Bridges, culverts, sewers, fish populations, and drinking water sources could be negatively impacted affected by the response of a stream channel to modification. Communication about the associated risk is critical to minimize effects on water resources and infrastructure. This article describes a vulnerability-criticality risk-logic matrix that can be used to determine the relative risk of stream modification projects. Risk assessment can aid practitioners in understanding and communicating the risk associated with modifying stream channels, and provide guidance for allocating resources to project maintenance or rehabilitation. Two examples are provided to demonstrate the use of the risk assessment.