This document provides guidelines for identifying stream instability problems at highway stream crossings and for the selection and design of appropriate countermeasures to mitigate potential damages to bridges and other highway components at stream crossings. The HEC-20 (Hydraulic Engineering Circular No. 20) manual covers geomorphic and hydraulic factors that affect stream stability and provides a step-by-step analysis procedure for evaluating stream stability problems. Guidelines and criteria for selecting countermeasures for stream stability problems are summarized, and the design of three countermeasures (spurs, guide banks, and check dams) is presented in detail. Conceptual design considerations for many other countermeasures are summarized.