This document specifies a method of determining discharge in open channels from observations of the surface slope and cross-sectional area of the channel.<\/p>\n
It is applicable to use under special conditions when direct measurement of discharge by typically more accurate methods, such as the velocity-area method, is not possible. Generally, the method can be used to determine discharge<\/p>\n
for a peak flow that left high-water marks along the stream banks,<\/p>\n<\/li>\n
for a peak flow that left marks on a series of water-level gauges or where peak stages were recorded by that series of gauges, and<\/p>\n<\/li>\n
for flow observed at the time of determining gauge heights from a series of gauges.<\/p>\n<\/li>\n<\/ol>\n
The method is commonly used to undertake the extension of stage\u2013discharge relationships above the highest gauged flows.<\/p>\n
It does not apply to determining discharges in tidal reaches.<\/p>\n
| PDF Pages<\/th>\n | PDF Title<\/th>\n<\/tr>\n | ||||||
|---|---|---|---|---|---|---|---|
| 2<\/td>\n | National foreword <\/td>\n<\/tr>\n | ||||||
| 7<\/td>\n | Foreword <\/td>\n<\/tr>\n | ||||||
| 8<\/td>\n | Introduction <\/td>\n<\/tr>\n | ||||||
| 9<\/td>\n | 1 Scope 2 Normative references 3 Terms and definitions 4 Principle of the method of measurement <\/td>\n<\/tr>\n | ||||||
| 11<\/td>\n | 5 Selection and demarcation of site 5.1 Initial survey of site 5.2 Selection of site 5.3 Demarcation of site <\/td>\n<\/tr>\n | ||||||
| 12<\/td>\n | 6 Measurement of slope 6.1 High-water marks 6.2 Crest-stage gauges 6.3 Pressure transmitters 6.4 Reference gauge 7 Determination of slope <\/td>\n<\/tr>\n | ||||||
| 13<\/td>\n | 8 Cross sections of a stream 8.1 Number and location of cross sections 8.2 Measurement of cross-sectional profiles 9 Computation of discharge 9.1 General 9.2 Uniform cross sections 9.2.1 General <\/td>\n<\/tr>\n | ||||||
| 14<\/td>\n | 9.2.2 Determination of the mean cross-sectional area and mean wetted perimeter of the reach 9.2.3 Determination of hydraulic radius <\/td>\n<\/tr>\n | ||||||
| 15<\/td>\n | 9.2.4 Determination of the mean velocity in the reach <\/td>\n<\/tr>\n | ||||||
| 16<\/td>\n | 9.3 Non-uniform cross sections (2-cross-section formulation) 9.3.1 General 9.3.2 Computation of conveyance 9.3.3 Evaluation of the friction slope <\/td>\n<\/tr>\n | ||||||
| 19<\/td>\n | 9.4 Composite cross sections <\/td>\n<\/tr>\n | ||||||
| 20<\/td>\n | 9.5 Computation of discharge using three or more cross sections <\/td>\n<\/tr>\n | ||||||
| 21<\/td>\n | 9.6 State of flow 10 Alternative methods to estimate conveyance 10.1 General 10.2 Divided channel method 10.3 Conveyance estimation system 11 Uncertainty in flow measurement 11.1 Definition of uncertainty <\/td>\n<\/tr>\n | ||||||
| 22<\/td>\n | 11.2 Sources of uncertainty for a uniform reach 11.2.1 General considerations 11.2.2 Uncertainty of the mean cross-sectional area <\/td>\n<\/tr>\n | ||||||
| 23<\/td>\n | 11.2.3 Uncertainty in the calculation of the mean wetted perimeter 11.2.4 Uncertainties in determination of the friction slope 11.2.5 Uncertainty due to the choice of the rugosity coefficient <\/td>\n<\/tr>\n | ||||||
| 24<\/td>\n | 11.2.6 Overall uncertainty in the measurement of discharge <\/td>\n<\/tr>\n | ||||||
| 25<\/td>\n | Annex A (informative) Approximate value of coefficients n and C for open channels <\/td>\n<\/tr>\n | ||||||
| 28<\/td>\n | Annex B (informative) Approximate value of Strickler-coefficients kSt for natural streams <\/td>\n<\/tr>\n | ||||||
| 30<\/td>\n | Annex C (informative) US Soil Conservation Service method of estimating Manning\u2019s n <\/td>\n<\/tr>\n | ||||||
| 32<\/td>\n | Annex D (informative) Conveyance estimation system <\/td>\n<\/tr>\n | ||||||
| 34<\/td>\n | Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Hydrometry. Slope-area method<\/b><\/p>\n |