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. . . The federal declaration activates the Federal Emergency Management Agency (FEMA) to assist the declared counties with response and recovery missions. In some cases, grants and low interest loans are made available to natural disaster victims. There is a USGS stream gage on Arroya De La Guna near Pleasanton, which is not far from the project area. The drainage area for the Arroyo De La Guna gage is approximately 405 square miles. According to the U.S. Geological Survey (USGS), the gage recorded a peak flow of 7,200 cfs on February 2, 1998. For comparison, the two highest annual peaks recorded for that gage were 11,400 cfs and 10,500 cfs in 1982 and 1983, respectively. The 1998 gaged peak flow is the 4th highest in the 41 year period of record for the gage. However, the worst flood and erosion damage due to high water in the arroyo was caused in 1998. Based on field measurements of a channel cross-section, high water marks, channel slope, and roughness values, it was estimated that the peak flow in the arroyo at the subject property was well over 10,000 cfs for the 1998 event. Based on the estimated peak flow of more than 10,000 cfs using field measurements (otherwise known as an indirect measurement), there is an apparent discrepancy between the USGS gaged flow and the indirect flow. The USGS was contacted and notified of the discrepancy, and said that the rating curve and peak flow for the gage would be investigated. An existing reservoir, Del Valle, located on Arroyo Valle upstream of Livermore, was reported to have filled to capacity during the high water period in February of 1998. California water officials reported that once the reservoir filled to capacity, all reservoir inflows were released or "passed through" the reservoir to prevent overfilling. The timing of the releases has not identified, so it is possible that the releases may not have helped to reduce the peak flood flows in the downstream arroyos. On the other hand, the reservoir may have helped the situation by storing inflows during the flood peaks if the release timing was appropriate. There is also a USGS stream gage on Arroyo Valle near Livermore that recorded a peak discharge of about 18,000 cfs in 1955. That discharge represents a maximwn annual peak during a 19 year period-of-record for that gage. The drainage area above the Arroyo Valle gage is approximately 147 square miles. III. HYDROLOGIC ANALYSIS Methodolol!V Existing floodplain information for Arroyo De La Guna is contained in the latest revision of the Alameda County Flood Insurance Study (FIS), which was published by the Federal Emergency Management Agency (FEMA)in September 1997. A copy of the FIS was obtained from FEMA, but the Flood Insurance Rate Maps were out of stock and unavailable at the time of this study. In addition to the FEMA information, flood discharge-frequency relationships for the subject arroyo were computed for this study by performing a statistical analysis of 41 years worth of gage data for the nearby streamflow gaging station. Computations were also made based on 2