STEPWISE PROCEDURE FOR EVALUATING STREAM STABILITY

Systematic analytical procedures for evaluation of stream stability typically are not readily available to the highway engineer. To remedy this, the purpose of this paper is to outline a stepwise analytical procedure that may be utilized to evaluate stream stability. The procedure incorporates three levels of analysis of increasing complexity and is somewhat similar to a three-part approach that was used in the early 1980's when the authors were employed at Simons, Li and Associates. Through the efforts of many, that procedure evolved into a valuable tool for stream stability analysis. For the FHWA Hydraulic Engineering Circular No. 20, "Stream Stability at Highway Structures," the three level approach was further refined and organized to include development of flow charts to assist in evaluation of stream stability at bridge crossings. The completion of each level of analysis results in an assessment of stream stability. Then, depending on the complexities of stream response or bridge design, the decision to proceed to the next level of analysis is made. The specific steps considered typical of Level 1 and Level 2 type analyses are outlined in this paper. The overall procedure provides a systematic approach to evaluation of stream stability at highway crossings, and will facilitate completion of such analyses by highway engineers.