John Dingman California Water Symposium 2008. Removal of natural storage, retention, and recycling...
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Transcript of John Dingman California Water Symposium 2008. Removal of natural storage, retention, and recycling...
John DingmanCalifornia Water Symposium 2008
Impacts of Urbanization on Peak Flow Using Remote Sensing
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
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.
Urban
Urban
Rural
Field MeasurementsConduct a cross-
sectional profile at two catchments
Measure high water marks and calculate peak flow.
MethodsRemote Sensing
To quantify area of developed landMeasure density of development.
Delineated Urban and Rural Watersheds 10 meter resolution
digital elevation model
Watershed Delineation
Urban Rural
Landsat 28 meter 6 band ImageryClassification of Developed and Non-
Developed LandsSpectral signatures:
VegetationBuildings , Roads
Remote Sensing Data
Landsat 28 meter 6 band ImageryClassification of Developed and Non-
Developed landsSpectral signatures:
VegetationBuildings , Roads
Remote Sensing Data – Maximum Likelihood Classification
Results: Maximum Likelihood Classification
Urban Rural
Results: Maximum Likelihood Classification
QT = KAaPb
QT = Peak Discharge (cfs)A = Drainage areaP = Mean annual basin-wide precipitationK,a,b are constants
Rantz Method
RI (years) Urban (cfs) Rural (cfs)
2 373 523
5 1051 1482
10 1619 2280
25 2343 3287
50 3401 4657
V = (1.49 * R0.67 S0.5)/ n
Rural Drainage BasinR = 3.28S = 2/3n = 0.05 - 0.10
Urban Drainage BasinR = 3.55S = 2/3n = 0.10 – 0.15
Mannings Equation – High Water Marks
Rural Drainage Basin
Urban Drainage Basin
Mannings Equation – High Water Marks
n = 0.05 n = 0.1
Velocity 53.9 27.0 ft/s
Q (peak flow) 5216.6 2608.3 cfs
n =0.1 n = 0.15
Velocity 28.4 19.0 ft/s
Q (peak flow) 8418.2 5612.2 cfs
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.
Conclusion