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STORM CHARACTERISTICS AND RAINFALL INFORMATION The summer storm that produced flooding in the Buffalo Creek area was a typical convective type cloudburst event. These events are not uncommon along the foothills and plains ea~t of the Continental Divide in Colorado. Storms like this fonn qcickly and can produce large amounts of rainfall, hail, and severe weather conditions within a short amount of time. At this time, only oreliminarv information is available describing the particular stornl over Buffalo Creek. The preliminary information is based on field analyses, rain gage information, and interviews with witnesses and local residents. The prelinunary information indicates that the storm moved from west to east and then stalled right over the lower part of the Buffalo Creek watershed. The most intense rainfall amounts, which fell over Buffalo Creek, are estimated to be from 2 inches to 3.5 inches within 30 to 90 minutes. The storm may have covered an area between 10 and 30 square miles. There is some uncertainty about the antecedent moisture conditions prior to the storm event. Some evidence suggests that there may have been up to a half inch or inch of rain within a few hours prior to the thunderstorm event, however there are conflicting reports from local residents. It is not necessarily unconunon for Buffalo CI1~ek to receive rainfall totaling 2 inches. However, the intensity or rate of the rain for this storm (heavy rain over a very short duration) may be a much less frequent event. To provide a point of [(,ference, the lOO-year, l-hoUI precipitation depth for southern Jefferson County is reported to be about 2.1 inches according to the Jefferson County Storm Drainage Design and Criteria Manual. To provide a more detailed reconstruction of the stonn ,~vent, all possible information i.s currently being collected from the National Weather Service, private meteorologists, and other entities. A reconstruction of the storm event from available radar images and other information is a necessary part of analyzing the storm event. This information will help describe the storm's track, areal extent, precipitation amounts, and intensities. Local residents have already been contacted to determine rainfall amounts based on individual rain gages. The collection and analysis of more detailed storm information is one of the most important elements in researching and reconstructing this event. HYDROLOGY AND HYDJltAUUCS Peak discharges for the July 12 event for the North Fork, Buffalo Creek, Sand Draw, and other tributaries were estimated by the USGS and the Colorado Water Conservation Board. The ewCB obtained detailed surveyed cross-sections on the North Fork, Sand Draw, and Buffalo Creek. The cross-section locations were carefully chosen to avoid places that had unusually high amounts of sediment deposition and places that may have had backwater or ponding effects from bridges or other features. High water marks and channel slopes were surveyed. Discharge estimates were made using Manning's equation with the collected field data. Since Manning's equation considers only clear-water discharge, some of the Manning's '''n'' values were adjusted upward (by 20% or 5