Extension of Rating Curves by Field Surveys

by Walter T. Sittner,

Serial Information: Journal of the Hydraulics Division, 1963, Vol. 89, Issue 2, Pg. 1-9

Document Type: Journal Paper


The need in modern river forecasting for station rating curves extending above the previous maximum flood is described. Two methods of computing rating extensions, based on field surveys, are given. The first, which is recommended for most sites, is the Stevens Method, presented by J. C. Stevens in 1907, and modified by the writer through inclusion of the Offset Technique. The second is the Slope-Conveyance Method. Basic differences between the extension of existing ratings and the development of entirely synthetic ratings are emphasized. The impact of these differences on the survey and computational methods is examined. An example is given of an actual rating extension by the Stevens Method, and the results are compare with those obtained by extending the same rating logarithmically. The point is made that a program of rating extensions based on field surveys is a vital and necessary part of any modern river forecasting program.

Subject Headings: Ratings | Geomatic surveys | Rivers and streams | Forecasting | Surveying methods | Curvature | Floods | Slopes

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