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r,n,'''-,'' II un.l (, 32.2 WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK ~11 - Method DescriotioDS ~2.11~ - Method A. Method A requires the collection of field data and' use of existing gaging station data. Visit all sites (stations and points of quantification) and measure channel cross sectional area and water surface slope. Method A requires substantial time and effort. ~2.11b - ~~. Method B also requires field visits to all points of quantification, but it entails somewhat less time and effort than Method A. Measure only ~hannel top width 'at bankfull stage in the field. ~2.11c - Method C. Method C requires the use of data that exists or can be developed from gaging station records, maps, photos, and similar sources and some visits to gaging stations for limited data collection. This method utilizes a relation- ship of basin characteristics to bankfull discharge. The relationship(s) is either developed locally or taken from United States Department of Interior (USDI) Geological Surveyor State reports. Examples of basin characteristics include area, precipitation, and mean or area-weighted elevation. ~2.'11d - Method D. Method D requires the use of data that exists or can be developed from gaging station records, maps, photos, and similar sources. Method D does not require field visits although some field verification is desirable. This method utilizes a relationship .between the log-Pearson type III peak flow, for the return interval most nearly equal to the return interval for the selected gage station bankfull discharge, and the watershed area or other appropriate basin characteristics. With the relationship developed, watershed area or other basin characteristics above the point of quanti- fication are used to directly calculate a log-Pearson type III peak flow approximately equivalent to bankfull discharge. ~2.11e - Method E. Apply Method E to those channel reaches which do not adjust their dimension in response to changes in frequent flows. An abbreviated flow requirement is developed which eliminates certain portions of the calculated channel maintenance hydrograph. ~ - Station Selection. All five analysis methods use certain basic relations to calculate bankfull discharge at the.ungaged point(s) of quantification. These relations are developed from the available gaging station data. Gaging stations used in this procedure will most commonly be operated by the United States *-FSH 4/89 AMEND 3-*