Senior Hydraulic Engineer Northwest Hydraulic Consultants, United States
Abstract Submission: Two-dimensional (2D) hydraulic modeling has become the preferred modeling approach for many agencies and practitioners. This presentation provides a brief overview of the differences between one-dimensional and 2D hydraulic modeling and then uses a current stream restoration project in Issaquah Creek near Issaquah, WA as a case study. The case study demonstrates conducting a hydraulic analysis and obtaining a Conditional Letter of Map Revision (CLOMR) from FEMA using Sedimentation and River Hydraulics - Two-Dimension (SRH-2D). As part of the project, in-stream restoration features are proposed along about 0.8 river miles of Issaquah Creek in Lake Sammamish State Park. Project goals include reconnecting the creek to its floodplain, providing quality habitat for native fish species, and supporting the ongoing riparian reforestation effort in the park.
The presentation will describe the proposed design and stream restoration features (e.g., complex wood structures, pilot channels, bank scrapes), and the hydraulic modeling completed for the project, which includes about 1.5 river miles of Issaquah Creek and its mouth at Lake Sammamish. A summary of various methods for representing the effects of large woody material in SRH-2D will be covered. In addition, floodplain mapping and floodway development using tools contained in Aquaveo’s Surface-water Modeling System (SMS) will be presented. Lastly, best practices for evaluating floodplain no-rise criteria and floodway surcharge regulations within SMS are also described.
