2019-10-28-minutes-public-works-study-session

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proposed conditions model is based on design surfaces (40 -foot hydraulic openings) that was provided by Jacobs to N HC in XML format. The topographic surfaces were imported into the Surface -water Modeling System (SMS) (Aquaveo, 2019). SMS is a computer program which provides a user interface for building and running hydraulic models, including SRH -21D. Utilizing the topographic surfaces, meshes were created for both existing and proposed conditions. A mesh is the computational domain of the hydraulic model and is utilized by SRH - 2D to calculate water depth, velocity, and other hydraulic parameters. The hydraulic model domain extends approximately 2,030 feet downstream and about 1,070 feet upstream of the existing NF Teanaway Road crossing. 4.1.2 Boundary Conditions The downstream boundary condition location was placed sufficiently far enough away from areas of interest to not influence the hydraulic results. The downstream boundary condition consists of water surface elevations that correspond to the mean recurrence interval of the peak flow being modeled. A sensitivity analysis on the downstream boundary condition was performed to obtain an accurate representation of the water surface profile (e.g. no rapid drawdown) and to determine if changes affected hydraulics through the areas of interest. To determine potential effects from flooding of the NF of the Teanaway River, FEMA water surface elevations for various floods on the NF of the Teanaway River were utilized to assess how they effect flooding of Lick Creek. Based on a sensitivity analysis of various water surface elevations at the confluence of Lick Creek and the NF of the Teanaway River, it was determined that FEMA flood elevations on the NF Teanaway River do not effect flood inundation limits or conveyance of the most downstream private property culvert (culvert 3 in Figure 2-3) or conditions upstream of this location. The upstream boundary condition defines inflow (see Section 3.2 for determination of peak flow estimates). The upstream boundary condition was placed sufficiently far enough away from the project site to not influence the hydraulic results at the NF Teanaway Road crossing. The inflow for all peak flow simulations was designated subcritical to match the expected flow regimes on Lick Creek at the boundary condition. The model was run in steady-state mode for all modeled simulations. Boundary conditions were also specified at the surveyed inlet and outlet of the existing culverts (Figure 2-3). This enabled SMS to interact with the Federal Highway Administration (FHWA) HY-8 culvert analysis software (FHWA, 2016) for calculating the hydraulics through the existing culverts. Geometric culvert data based on the Kittitas County survey were incorporated into the model. Based on direction from Kittitas County, the culverts for both existing and proposed conditions were assumed to be unobstructed from debris and ice. Therefore, the modeling of obstructions on existing culverts is beyond the scope of this analysis. It is important to note that as the project progresses, a risk-based approach can be completed using the hydraulic model as a tool to assess varying hydrology, structure openings, and evidence of previous flooding experienced by property owners. Once an existing North Fork Teanaway Road - Lick Creek Fish Passage Enhancement Project 10 Flood Rise Analysis — Maintaining Creek Flows Along Teanaway Road