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Flood Frequency

OSW Memos

SW 73.16 States current policy regarding (1) publication of frequency characteristics for recurrence intervals longer than twice the period of record, (2) definition of flood characteristics at a gaged site either by probability analysis of the gage record or by a regional relation, (3) minimum sample size for use in regression analyses, and (4) adherence to, and latitude to deviate from, established guidelines for hydrologic interpretations.
SW 75.16 Identifies appropriate uses for a procedure to estimate flow characteristics from channel size; presents guidelines for data collection, analysis and application; emphasizes field guidance by qualified consultant; encourages improvement in methodology; and reaffirms coordinating functions of the Surface Water Branch.
SW 76.03 Updating streamflow/basin characteristics file. Provides reminder to update streamflow characteristics, such as the T-year floods, in the streamflow/basin characteristics file when the log-Pearson Type III frequency curves are developed in flood-frequency or low-flow studies.
SW 76.07 Announces forthcoming release and describes use and content of new Water Resources Council (WRC) report "Guidelines for determining flood-flow frequencies" that will supercede WRC Bulletin 15. [an error occurred while processing this directive]
SW 77.02 Transmits reprint of an article from the Journal of Research of the U. S. Geological Survey entitled "Confidence limits for flood-frequency curves computed from samples from Pearson Type III populations."
SW 77.03 Reiterates policy that determination of "probable maximum flood" has little value in the evaluation of flood hazards and is therefore outside the scope of the WRD mission. See update SW 83.05.
SW 77.04 Encloses an announcement describing the availability of flood-frequency data at District offices and establishes policy for responding to requests for such information. [an error occurred while processing this directive]
SW 77.07 Distributes report "Flood-frequency--expected and unexpected probabilities" that compares the attributes and characteristics of flood-frequency curves computed with and without an expected probability adjustment.
SW 77.17 Revises limitations on the publication and distribution of estimated flood-frequency information. Supersedes SWB 69.11, 70.05, 73.16, and 76.07. See update SW 89.12.
SW 78.05-2 Transmits guidelines on entering synthesized flow data into the Streamflow and Basin Characteristics computer file. Provides guidance on entry of synthesized or derived flow records into the streamflow and basin characteristics computer file. [an error occurred while processing this directive]
SW 79.01 Transmits the report "A rainfall-runoff modeling procedure for improving estimates of T-year floods for small drainage basins" and notes the usefulness of the maps and relations presented in the report.
SW 80.02 Advises Districts to prepare for adequate coordination and cooperation with other federal agencies during flood emergencies. Lists 1974-76 National Weather Services (NWS) rating extension sites of the NWS Flood Forecast Centers. [an error occurred while processing this directive]
SW 81.01 Transmits report "Review and evaluation of urban flood-flow frequency procedures" that provides a concise and comprehensive review of techniques for estimating flood peaks and/or hydrographs for ungaged urban areas.
SW 82.04 Transmits WRC Bulletin 17-B
SW 82.10 Transmits and discusses the report "Techniques for estimating flood hydrographs for ungaged urban watersheds."
SW 83.05 Reiterates policy expressed in SW 77.03, that the determination of "probable maximum flood" is outside the scope of the WRD mission. [an error occurred while processing this directive]
SW 84.04 Transmits guidelines and specifications for flood-insurance studies. Lists WRD offices receiving Federal Emergency Management Agency (FEMA) guidelines.
SW 86.07 Transmits report "Simulation of flood hydrographs for Georgia streams" -- simplified method of estim,ating flood hydrograph using basin lag and T-year peak flow.
SW 87.01 Transmits report on feasibility of assigning a probability to the probable maximum flood.
SW 87.08 New procedures for hydrologic regression and network analysis using generalized least squares.
SW 88.06 Discusses status of "Bulletin 17B" flood-frequency guidelines and gives the results of a survey of problems encountered in using the guidelines.
SW 88.07 States guidelines for the operation of crest-stage programs. [an error occurred while processing this directive]
SW 88.08 Transmits and discusses the National Research Council report on estimating probabilities of extreme floods.
SW 89.12 Revises SW 77.17 limitations on publication and distribution of estimated flood-frequency information. Allows estimation and publication of discharges with recurrence intervals of up to 500\x11years. [an error occurred while processing this directive]
SW 90.09 Provides information and tables summarizing WRD's involvement in local flood-warning systems.
SW 91.10 Provides a list of salient papers describing the use and illustrating the potential applications of dendrogeomorphic analysis.
SW 92.09 Explains the procedures for determining and applying adjustments to discharge measurements made at a distance from the gaging station during periods of changing stage and discharge.
SW 92.10 Provides guidelines for identifying and evaluating peak-discharge errors.
SW 92.11 States the importance of flow-process identification in mountain streams and provides guidance on how to properly identify flow processes, particularly when debris flows are possible. [an error occurred while processing this directive]
SW 95.02 Announces the availability of WRIR 94-4002, "Nationwide summary of U.S. Geological Survey regional regression equations for estimating magnitude and frequency of floods for ungaged sites." The report contains a PC diskette of version 1.1 of the USGS National Flood Frequency program, including regression equations and procedures for estimating flood hydrographs.

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