Welcome to ROSA P |
Stacks Logo
Advanced Search
Select up to three search categories and corresponding keywords using the fields to the right. Refer to the Help section for more detailed instructions.
 
 
Help
Clear All Simple Search
Advanced Search
Improving techniques to estimate the magnitude and frequency of floods on urban streams in South Carolina, North Carolina, and Georgia, 2011 (ver. 1.1, March 2014) : U.S. Geological Survey scientific investigations report 2014-5030.
  • Published Date:
    2014-03-01
  • Language:
    English
Filetype[PDF-5.96 MB]


This document cannot be previewed automatically as it exceeds 5 MB
Please click the thumbnail image to view the document.
Improving techniques to estimate the magnitude and frequency of floods on urban streams in South Carolina, North Carolina, and Georgia, 2011 (ver. 1.1, March 2014) : U.S. Geological Survey scientific investigations report 2014-5030.
Details:
  • Corporate Creators:
  • Resource Type:
  • ISSN:
    2328-0328
  • Edition:
    Version 1.1, March 2014
  • Corporate Publisher:
  • Abstract:
    Reliable estimates of the magnitude and frequency

    of floods are essential for the design of transportation and

    water-conveyance structures, flood-insurance studies, and

    flood-plain management. Such estimates are particularly

    important in densely populated urban areas. In order

    to increase the number of streamflow-gaging stations

    (streamgages) available for analysis, expand the geographical

    coverage that would allow for application of regional

    regression equations across State boundaries, and build

    on a previous flood-frequency investigation of rural U.S.

    Geological Survey streamgages in the Southeast United

    States, a multistate approach was used to update methods for

    determining the magnitude and frequency of floods in urban

    and small, rural streams that are not substantially affected by

    regulation or tidal fluctuations in Georgia, South Carolina,

    and North Carolina. The at-site flood-frequency analysis

    of annual peak-flow data for urban and small, rural

    streams (through September 30, 2011) included 116 urban

    streamgages and 32 small, rural streamgages, defined in

    this report as basins draining less than 1 square mile. The

    regional regression analysis included annual peak-flow

    data from an additional 338 rural streamgages previously

    included in U.S. Geological Survey flood-frequency reports

    and 2 additional rural streamgages in North Carolina that

    were not included in the previous Southeast rural floodfrequency

    investigation for a total of 488 streamgages

    included in the urban and small, rural regression analysis.

    The at-site flood-frequency analyses for the urban and small,

    rural streamgages included the expected moments algorithm,

    which is a modification of the Bulletin 17B log-Pearson

    type III method for fitting the statistical distribution to the

    logarithms of the annual peak flows. Where applicable,

    the flood-frequency analysis also included low-outlier and

    historic information. Additionally, the application of a

    generalized Grubbs-Becks test allowed for the detection of

    multiple potentially influential low outliers.

    Streamgage basin characteristics were determined

    using geographical information system techniques. Initial ordinary least squares regression simulations reduced the

    number of basin characteristics on the basis of such factors

    as statistical significance, coefficient of determination,

    Mallow’s Cp statistic, and ease of measurement of the

    explanatory variable. Application of generalized least

    squares regression techniques produced final predictive

    (regression) equations for estimating the 50-, 20-, 10-, 4-,

    2-, 1-, 0.5-, and 0.2-percent annual exceedance probability

    flows for urban and small, rural ungaged basins for three

    hydrologic regions (HR1, Piedmont–Ridge and Valley; HR3,

    Sand Hills; and HR4, Coastal Plain), which previously had

    been defined from exploratory regression analysis in the

    Southeast rural flood-frequency investigation. Because of the

    limited availability of urban streamgages in the Coastal Plain

    of Georgia, South Carolina, and North Carolina, additional

    urban streamgages in Florida and New Jersey were used in

    the regression analysis for this region. Including the urban

    streamgages in New Jersey allowed for the expansion of the

    applicability of the predictive equations in the Coastal Plain

    from 3.5 to 53.5 square miles. Average standard error of

    prediction for the predictive equations, which is a measure

    of the average accuracy of the regression equations when

    predicting flood estimates for ungaged sites, range from

    25.0 percent for the 10-percent annual exceedance probability

    regression equation for the Piedmont–Ridge and Valley

    region to 73.3 percent for the 0.2-percent annual exceedance

    probability regression equation for the Sand Hills region.

  • Format:
  • Main Document Checksum:
  • Supporting Files:
    No Additional Files
No Related Documents.
You May Also Like: