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Where affected drainage basins and subbasins included various burn severities and unburned areas, post- burn RCNs were area-weighted by the percentage of each burn type. A summary of post-burn calibration data (RCNs, abstractions, lag-time factors) for all Willow Creek subbasins is listed in Appendix table lb. Table 2 shows the 6 Willow Creek basins that were modeled and the results of the post-burn runoff calibrations. Long-Term Recovery Hydrology Long-term recovery of burned watersheds is based on a method developed in Elliott and others (2005). Hydrologic responses in Willow Creek were computed to evaluate peak flows at a point in the post-burn, long-term recovery period (Phase 3). Hydrologic responses during the post-fire recovery period are estimated in the Willow Creek burned areas based on the following assumptions: 1. A wildfire will raise the RCN in a burned drainage basin from a pre-fire RCN to a post-fire RCN as a function of burned area and severity. 2. During the recovery period, the value of the larger post-fire RCN will attenuate with time and eventually approach, or decay to, the value of the smaller pre-fITe RCN. 3. Although it is recognized as a simplification, for the purposes of this report, recovery will be characterized as a decay function that reduces the post-fire RCN with time. 4. Initial decay will be the most rapid and will take place as a function of the magnitude of the pre-fire RCN and the difference between pre- and post-fire RCN's. The post-fire recovery equation used in this study is a function of initial RCN, change in RCN (due to wildfire), and time. The equation has the form of an exponential decay equation that can be used to estimate an RCN at any point in the recovery process. In this analysis, the equation (Elliott and others, 2005) was used to develop estimates for parameters used in the HEC-l and HEC-HMS models, and the models were then used to develop a time series of annual flood peaks of the 100-year design storm to characterize long-term recovery. The resultant time-series values were evaluated to identify a time in the recovery process when the change in estimated 100-year flood peak became less than 5 percent, per year, of the RCN change due to wildfire. At Willow Creek, the long-term recovery hydrology was estimated to be in effect after about 5 years (Elliott and others, 2005). HEC-HMS input parameters (U.S. Army Corps of Engineers, 2001b) for individual subbasins were calculated for year 5 to enable HEC-HMS modeling of peak flows (Appendix table lc. Discharge results from these analyses were used as input for hydraulic analysis. Peak discharges were not bulked assuming that recovery flows would not contain large sediment loads. The recovery parameters also were used with the 10-, 50-, and 500-yr rainfall amounts to compute peak discharges for the corresponding peak discharge recurrence intervals (table 3).