Designing Riverbank Armoring to Withstand Extreme Flows - A Case Study on the Mendenhall River in Juneau, Alaska

Author: Kaylin Pettijones, RESPEC and Jake Ciufo.

Video Presentation

Abstract

Many riverine and coastal communities today are impacted by accelerating erosion and frequent flooding. In Juneau, properties adjacent to the Mendenhall River are threatened by annual Glacial Lake Outburst Flooding (GLOF). GLOF is a phenomenon in which a glacial lake forces the damming glacier to uplift, instantaneously releasing the dammed lake. In recent years, Juneau has seen GLOF cause extremely large flows on the Mendenhall, surpassing the 500-year flood and causing a FEMA major disaster declaration. To combat future property loss associated with GLOF events, various forms of armoring have been deployed along this riverbank; however, GLOF flow regimes are unique, evolving, and severe, making the design of bank stabilization to withstand such events challenging. Through a case study on the Mendenhall, this talk presents the decision- making process, analysis, and design methods required when engineering riverbanks to be resilient against extreme flow regimes and hydraulic conditions. To accurately account for the high GLOF flowrates during design and permitting, nonstandard hydrologic methods were required and both 1D and 2D HEC-RAS modeling approaches were applied in tandem. The final design was developed to adhere to physical constraints requested by the client and to withstand the severe flowrates now regularly experienced on the Mendenhall River.

Citation

Please use the following citation when citing this presentation: