ISO TR 9210-2017 pdf free.Hydrometry — Measurement in meandering river and in streams withunstable boundaries.
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document(including any amendments) applies.
ISO 772,Hydrometry —Vocabulary and symbols
For the purposes of this document, the terms and definitions given in ISo 772 and the following apply.
river, which flows through alluvium, formed from its own deposits
Note 1 to entry: The sediment carried by an alluvial river, except for the wash load, is similar to that in the bed.3.2
braided river:river characterized by a wide and shallow open channel, in which flow passes through a number ofsmall-interlaced channels separated by shoalsNote 1 to entry: Frequently, there is little or no erosion of the main banks of a braided river.Note 2 to entry: Generally, there is little or no meandering of the main channel of a braided river, but meanderingin the minor channels is usual.
meandering river:channel following a sinuous path, characterized by curved flow leading to bank erosion alternatingwith shoaling
transitioncrossover:inflection reach between two meander loops in which the main flow crosses from one side of thechannel to the other
Note 1 to entry: The depth of flow in a transition is usually reduced from normal depth and is more uniform thanin the curved reach.
However,when the flow directions during flood and low flow seasons are very different,itpermissible to suitably adjust the orientation of gauging section during that season, taking into accounthe requirements in IS0 748:2007,5.1 a) and b).
ISO 748:2007,5.1 b) further states that the accuracy of the determination of discharge is increased ifthe flow directions for all points on any vertical are parallel to one another, and at right angles to themeasurement section.
ISO 748:2007,5.1 c) recommends that the bed and the margins of the channels should be stable anwell-defined at all stages of flow in order to facilitate accurate measurement of the cross-section, and toensure uniformity of conditions during and between discharge measurements.
At a measuring site, even if properly located to satisfy these requirements during flood season, the flowdirection can change appreciably during low water season.As far as possible, the basic stream gaugingsection should not be changed.However, when the flow directions during flood and low water seasonsare very different, it is permissible to suitably adjust the orientation of gauging section during the lowwater season, taking into account the requirements in ISO 748:2007,5.1 a) and b).ISO TR 9210 pdf download.