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CARRIAGE HILLS NO. 2 DAM, Dam Failure Forensic Investigation Report Page 29 February 27, 2015 estimated by the USBR using reservoir stage data along with measured outlet gate openings throughout the storm. Using the storage and outflow hydrographs, Jacobs was able to estimate the Lake Estes inflow hydrograph for the Sept. 2013 flood. This combined inflow hydrograph does not differentiate between various sources of inflow to Lake Estes, so all subbasins, including Fish Creek, were calibrated uniformly. Caution needs to be exercised in using model results from individual subbasins (e.g. Fish Creek) since they were not individually calibrated. Jacobs reports that they calibrated the model to best‐fit basin‐wide peaks, so as not to overly rely on individual observed or estimated peak flows. They cited Robert Jarrett’s work and a USGS report (Godt et. all, 2013) in concluding that surge flows from sudden failures of debris dams, embankment dams, road embankments, etc. all played a major role in some peak flows during the Sept. 2013 flood. Their HEC‐HMS model is solely a rainfall‐runoff model and is not intended to reproduce dam breaks or surge flows. The Jacobs model shows Fish Creek peaking around 2000 cfs on Sept. 12, 2013 at 1400 hrs (MDT), which was after the storm’s second large spike in rain intensity (Figure 21). The model shows a second lower peak of 1900 cfs on Fish Creek on Sept. 13, 2013, around 0200 hrs, which is after the third and final large spike in rain intensity. The Jacobs model also shows that large inflows to Lake Estes (peak inflow of 5280 cfs) in the early morning of Sept. 13th could have been explained by rain‐driven runoff on the mainstem Big Thompson (model Reach R330, peak 3500 cfs) (see Figure 22). DWR’s Big Thompson Above Lake Estes (BTABESCO) stream gage gave a peak flow of around 3000 cfs on Sept. 13th, between 0000 and 0600 hrs. Figure 21: CDOT/Jacobs HEC‐HMS model Sept. 2013 Fish Creek hydrograph (model subbasin BT05) in Universal Coordinated Time (UTC).