Techniques for estimating monthly mean Streamflow at gaged sites and monthly Streamflow duration characteristics at ungaged sites in central Nevada were developed using Streamflow records at six gaged sites and basin physical and climatic characteristics. Streamflow data at gaged sites were related by regression techniques to concurrent flows at nearby gaging stations so that monthly mean streamflows for periods of missing or no record can be estimated for gaged sites in central Nevada. The standard error of estimate for relations at these sites ranged from 12 to 196 percent. Also, monthly Streamflow data for selected percent exceedence levels were used in regression analyses with basin and climatic variables to determine relations for ungaged basins for annual and monthly percent exceedence levels. Analyses indicate that the drainage area and percent of drainage area at altitudes greater than 10,000 feet are the most significant variables. For the annual percent exceedence, the standard error of estimate of the relations for ungaged sites ranged from 51 to 96 percent and standard error of prediction for ungaged sites ranged from 96 to 249 percent. For the monthly percent exceedence values, the standard error of estimate of the relations ranged from 31 to 168 percent, and the standard error of prediction ranged from 115 to 3,124 percent. Reliability and limitations of the estimating methods are described.

acre-foot (acre-ft) 1233 cubic meter cubic foot per second (ft 3 /s) 0.02832 cubic meter per second foot (ft) 0.3048 meter inch (in.) 25.4 millimeter mile (mi) 1.609 kilometer square mile (mi 2 ) 2.590 square kilometer Temperature: Degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) by using the formula °F = [1.8 (°C)] + 32. Degrees Fahrenheit can be converted to degrees Celsius by using the formula °C = 0.556 (°F − 32).

Information is presented for estimating the magnitude and frequency of floods on streams in South Carolina. Flood-frequency characteristics for 151 gaging stations were related to basin characteristics by multiple regression techniques for each of four physiographic provinces. Equations were derived to estimate flood magnitudes at recurrence intervals ranging from 2 to 100 years on streams with drainage areas greater than 1.0 square mile. Examples demonstrate the procedure for computing flood-frequency discharge for sites on gaged and ungaged streams in South Carolina. Relationships of flood discharge and frequency to drainage area are presented for the main stem of major streams. A compilation of flood records for gaging stations in South Carolina is presented as supplemental data.

A typical (average) flood hydrograph corresponding to a peak discharge of specific recurrence interval can be simulated for ungaged rural basins having drainage areas less than 500 square miles in South Carolina. Three dimensionless hydrographs were developed on the basis of data collected during 188 storm events at 49 stations representing a wide range of drainage area sizes and basin conditions. The design peak discharge and a volumeadjusted average basin lagtime are required to apply the technique. The standard errors of estimate for simulated hydrograph widths at 50 and 75 percent, respectively, of observed stormflow were ±14.1 and ±18.3 percent for basins in the Blue Ridge physiographic province, ±29.2 and ±36.2 percent for basins in the Piedmont province, and ±17.8 and ±22.8 percent for basins in the Upper and Lower Coastal Plain subprovinces.Multiple-regression analyses were used to develop equations for estimating average basin lagtime. At the 95-percent confidence level, drainage area was determined to be the only significant explanatory variable needed to estimate the average lagtime for basins in each physiographic province. The standard error of estimate of regression relations developed for estimating lagtimes for the Blue Ridge and Piedmont provinces, and the Upper Coastal Plain and Lower Coastal Plain subprovinces were ±7.3, ±25.6, ±34.3, and ±25.6 percent, respectively.A regression equation that provides runoff volume in inches also was developed. The explanatory variables used in the equation for estimating runoff volume are peak discharge, average basin lagtime, and drainage area*, the standard errors of estimate of equations applicable in the Blue Ridge, Piedmont, Upper Coastal Plain, and Lower Coastal Plain were ±10.3, ±21.1, ±13.6, and ±15.1 percent respectively. The regression equations for estimating runoff volume are the basis of an adjustment to average basin lagtime, which is required to simulate flood hydrographs by use of the dimensionless hydrographs.The simulation techniques and regression equations may be useful engineering tools for estimation where time of inundation or storage of floodwater is a part of the flood prevention or structure design criteria.

Devastating floods throughout northern California and western Nevada occurred January 1-3. 1997. In Nevada alone, about $500 million in projected damages and two deaths were attributed to floodwaters along the Truckee, Carson, and Walker Rivers (fig. 1) (Nevada Appeal, 1997). Flooding was extensive in downtown Reno (fig. 2), at the Reno/Tahoe International Airport, and in the industrial area of Sparks, Nev. (fig. 3).