Estimation of peak discharge quantiles for selected annual exceedance probabilities in Northeastern Illinois.

Details

• Creators:
  Over, Thomas M. ; Saito, Riki ; Veilleux, Andrea G. ; Sharpe, Jennifer ; Soong, David ; Ishii, Audrey
• Corporate Creators:
  Geological Survey (U.S.) ; United States. Department of the Interior
• Corporate Contributors:
  Illinois. Department of Transportation. Bureau of Materials and Physical Research ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Floods
  • Urbanization
  • Peak discharge
  • Streamflow
  • Drainage basins
  • Land use
  • Regression analysis
  • Web applications
  • Spatial analysis
  • Flood frequency
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• Publication/ Report Number:
  FHWA-ICT-16-013
• Resource Type:
  Tech Report
• Geographical Coverage:
  Illinois ; United States
• Corporate Publisher:
  Illinois Center for Transportation
• Abstract:
  This report provides two sets of equations for estimating peak discharge quantiles at annual exceedance probabilities (AEPs) of 0.50, 0.20, 0.10, ; 0.04, 0.02, 0.01, 0.005, and 0.002 (recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively) for watersheds in Illinois based ; on annual maximum peak discharge data from 117 watersheds in and near northeastern Illinois. One set of equations was developed through a ; temporal analysis with a two-step least squares-quantile regression technique that measures the average effect of changes in the urbanization ; of the watersheds used in the study. The resulting equations can be used to adjust rural peak discharge quantiles for the effect of urbanization, ; and in this study the equations also were used to adjust the annual maximum peak discharges from the study watersheds to 2010 urbanization ; conditions. ; The other set of equations was developed by a spatial analysis. This analysis used generalized least-squares regression to fit the peak discharge ; quantiles computed from the urbanization-adjusted annual maximum peak discharges from the study watersheds to drainage-basin ; characteristics. The peak discharge quantiles were computed by using the Expected Moments Algorithm following the removal of potentially ; influential low floods defined by a multiple Grubbs-Beck test. To improve the quantile estimates, generalized skew coefficients were obtained ; from a newly developed regional skew model in which the skew increases with the urbanized land use fraction. The drainage-basin ; characteristics used as explanatory variables in the spatial analysis include drainage area, the fraction of developed land, the fraction of land ; with poorly drained soils or likely water, and the basin slope estimated as the ratio of the basin relief to basin perimeter. ; This report also provides: (1) examples to illustrate the use of the spatial and urbanization-adjustment equations for estimating peak discharge ; quantiles at ungaged sites and to improve flood-quantile estimates at and near a gaged site; (2) the urbanization-adjusted annual maximum ; peak discharges and peak discharge quantile estimates at streamgages from 181 watersheds including the 117 study watersheds and 64 ; additional watersheds in the study region that were originally considered for use in the study but later deemed to be redundant. ; The urbanization-adjustment equations, spatial regression equations, and peak discharge quantile estimates developed in this study will be ; made available in the web-based application StreamStats, which provides automated regression-equation solutions for user-selected stream ; locations. Figures and tables comparing the observed and urbanization-adjusted peak discharge records by streamgage are provided at ; http://dx.doi.org/10.3133/sir20165050 for download.
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• Format:
  PDF
• Funding:
  R27-144
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/31071/dot_31071_DS1.pdf
• File Type:
  [PDF - 7.57 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:c2d6fba6a5d949169791c833603054f4afbcb74799c059b561efe001856453bd