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4 HYDROLOGIC ANALYSIS <br />There are no published or current streamflow gages on Lick Creek, or a nearby similar watershed, which <br />could be used for determining peak streamflow values at the project site. Previous studies at the NF <br />Teanaway Road crossing, documented in technical memorandums completed by Watershed Science & <br />Engineering (2012) and the FHWA (2017), were however available to review. Modeled peak flow values <br />for both of these studies were calculated using the now out-of-date USGS Region 5 Regression <br />Equations, documented in Sumioka et al. (1998). The 100 -year peak flow modeled in these studies was <br />287 cubic feet per second (cfs). <br />To utilize the best available methods for this project, NHC used the most current USGS Region 2 <br />Regression Equations, which were updated in 2016 (Mastin et al., 2016), to determine peak flows at the <br />NF Teanaway Road crossing. SteamStats, the commonly used USGS online application, was utilized to <br />calculate peak flow estimates with the USGS Region 2 Regression Equations. SteamStats determines <br />inputs to be used in the USGS Region 2 Regression Equations, such as basin area, canopy cover, and <br />precipitation (USGS, 2016; Section 3.1). The basin canopy cover from Stream5tats was 52.7%, based on <br />the 2001 National Land Cover Database, which was prior to the Lick Creek Fire in 2005 and the Jolly <br />Mountain Fire in 2017. The estimated peak flows and associated standard error of prediction with the <br />2001 canopy cover are summarized in Table 4.1, under USGS StreamStats. <br />Per direction from KCPW during project scoping, post -fire impacts were not to be directly assessed for <br />determining hydrology. However, due to the uncertainty in hydrology, geomorphology, and hydraulics <br />(e.g., USGS Region 2 Regression Equation's standard errors, ongoing restoration efforts in the upper <br />watershed, potential for debris and ice blockages at culverts, etc.), NHC evaluated more recent canopy <br />cover values. To evaluate canopy cover changes within the basin, including fires that have occurred since <br />the canopy cover was estimated in 2001, NHC used aerial imagery from October 15, 2017 to estimate an <br />20 North Fork Teanaway Road — Lick Creek Fish Passage Enhancement Project <br />Hydraulics Basis of Design <br />