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The effects of urbanization on floods in the Austin metropolitan area, Texas
This report looks at compiled data from 1956-1980 to "provide a technique for estimating the magnitude and frequency of flood-peak discharges at ungaged sites and to estimate the effects of changes in urbanization on flood peaks."The effects of urbanization on flood peaks in streams in the Austin metropolitan area were studied in two separate analyses. In the first analysis, annual peak discharge records at 13 streamflow-gaging sites were used to compute a recorded flood frequency relation for each site. Rainfall and streamflow data for 10 to 20 storms for each of these sites were used to calibrate a rainfall-runoff model in which a 55-year rainfall record was used to simulate 55 annual peak discharges. These simulated discharges also were used to develop a flood-frequency relation at each site. The flood-frequency relations from recorded and generated data were then combined by weighting the recorded flood frequency by the years of record at each site to produce a combined (or weighted) flood frequency at each site. Flood frequencies for all 13 sites were subsequently regressed against basin characteristics at each site to determine possible effects of urbanization.
The regression analysis of the combined flood-frequency data for the 13 sites yielded an equation for estimating floods of a given recurrence interval at ungaged sites in the Austin area as a function of the contributing drainage area, the total impervious area percentage, and basin shape. The regression equation estimates that a near fully developed hypothetical drainage basin (impervious area percentage, 45) would have discharges for the 2- and 100-year recurrence interval that are 99 percent and 73 percent greater, respectively, than discharges for those frequencies from a rural drainage basin (impervious percentage, 0).
In the second analysis, records at one streamflow-gaging site on Waller Creek were analyzed for changes in rainfall-runoff and flood-frequency relations due to urbanization. Annual peak discharges from 1956 to 1980 and data from a total of 80 storms at the Waller Creek site were analyzed. Both analyses showed increases comparable to those predicted using the equations developed from the 13-station analysis. The last 14 years of record (the near fully developed land-use stage for the Waller Creek analysis) at the two sites on Waller Creek were part of the 13-station analysis.
The U.S. Geological Survey, in cooperation with the Texas Department of Water Resources began limited investigations of urban watersheds in Austin in 1954, with the installation of two streamflow-gaging stations and three recording rain gages in the Waller Creek watershed. In 1963, a streamflow gage and three recording rain gages were installed at Wilbarger Creek watershed, a rural area just north of Austin. In cooperation with the City of Austin, the urban study was expanded in 1975 to include additional streamflow and rainfall gaging stations and the collection of surface water-quality data. The number of streamflow-gaging stations increased from 2 to 25 and the number of recording
rain gages increased from 3 to 31.Waller Creek Working Grou
Statistically Locked-in Transport Through Periodic Potential Landscapes
Classical particles driven through periodically modulated potential energy
landscapes are predicted to follow a Devil's staircase hierarchy of
commensurate trajectories depending on the orientation of the driving force.
Recent experiments on colloidal spheres flowing through arrays of optical traps
do indeed reveal such a hierarchy,but not with the predicted structure. The
microscopic trajectories, moreover,appear to be random, with commensurability
emerging only in a statistical sense. We introduce an idealized model for
periodically modulated transport in the presence of randomness that captures
both the structure and statistics of such statistically locked-in states.Comment: REVTeX with EPS figures, 4 pages, 4 figure
High fat diet causes rebound weight gain
Acknowledgements This work was funded by a grant from Action Medical Research (SP4581). We are grateful to the animal house staff for looking after the animals.Peer reviewedPublisher PD
Ultra-Light Scalar Fields and the Growth of Structure in the Universe
Ultra-light scalar fields, with masses of between m=10^{-33} eV and
m=10^{-22} eV, can affect the growth of structure in the Universe. We identify
the different regimes in the evolution of ultra-light scalar fields, how they
affect the expansion rate of the universe and how they affect the growth rate
of cosmological perturbations. We find a number of interesting effects, discuss
how they might arise in realistic scenarios of the early universe and comment
on how they might be observed.Comment: 12 pages, 11 figure
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