1. John Dingman California Water Symposium 2008

2. Removal of natural storage, retention, and recycling of precipitation Runoff Groundwater recharge Widening of stream channels Floodwater velocities In the magnitude and frequency of flooding Channel morphology changes because of the altered hydrology (Anacostia, 1991). The influence of impervious materials on urban development leads to: Center for Watershed Protection

3. City of San Ramon The population has increased 11% and the number of housing units increased 13% in 2006 (Demographics Research Unit 2007). New development in the urban watershed is called Windemere, which began in 2001.

4. Urban Rural

5. Field Measurements Conduct a cross-sectional profile at two catchments Measure high water marks and calculate peak flow. Remote Sensing To quantify area of developed land Measure density of development.

6. Delineated Urban and Rural Watersheds 10 meter resolution digital elevation model Urban Rural

7. Landsat 28 meter 6 band Imagery Classification of Developed and Non-Developed Lands Spectral signatures: Vegetation Buildings, Roads

8. Landsat 28 meter 6 band Imagery Classification of Developed and Non-Developed lands Spectral signatures: Vegetation Buildings, Roads

9. Urban Rural

11. Q T = KA a P b Q T = Peak Discharge (cfs) A = Drainage area P = Mean annual basin-wide precipitation K,a,b are constants RI (years)Urban (cfs)Rural (cfs) 2373523 510511482 1016192280 2523433287 5034014657

12. V = (1.49 * R 0.67 S 0.5 )/ n Rural Drainage Basin R = 3.28 S = 2/3 n = 0.05 - 0.10 Urban Drainage Basin R = 3.55 S = 2/3 n = 0.10 – 0.15

13. Rural Drainage Basin Urban Drainage Basin n = 0.05n = 0.1 Velocity53.927.0ft/s Q (peak flow)5216.62608.3cfs n =0.1n = 0.15 Velocity28.419.0ft/s Q (peak flow)8418.25612.2cfs

14. Based on the high water marks in the Urban Drainage Basin the calculated flow suggest greater than a 50 year RI for the largest peak flow (mid-January). The Rural Drainage Basin was 10-50 years RI. The development in the Tassajara Valley, with the use of impervious materials, may be increasing the peak flow of the streams.