ISO 1070:2018 pdf free

ISO 1070:2018 pdf free.Hydrometry一Slope-area method
The three formulae and associated friction coefficients are employed best in streams or rivers with a uniform or slightly constricting reach in which the cross-sectional profile and bed material are consistent throughout the reach. The use of this method in non-uniform reaches, composite cross sections (a main channel and one or more overflow sections), and/or changes in channel geometry and roughness factors will introduce additional uncertainty in the computations.
It is recommended that approximate measurements of widths, depths and surface slopes be made in a preliminary survey to decide whether the site is suitable and conforms (to the extent possible) with the conditions specified in 5.2 and 5.3. Interviews with witnesses, if any, should be done to get information about the flood timing, flow paths, high water levels, and possible bed changes during the event, and to ascertain the availability of photographs or videos of the flood event.
Ideally, the river reach should be straight, and should contain no large curvatures or meanders. There should not be any abrupt change in the bed slope in the measuring reach, as can occur in steep, rocky channels. The cross section should be as uniform as possible or slightly constricting throughout the reach and free from obstructions. Preferably, vegetation should be minimal and distributed uniformly throughout the reach. Ideal reach conditions are rare, so a reach with the best combination of desirable characteristics should be chosen.
Good high-water mark definition is essential to the slope-area method. The presence and quality of high-water marks are therefore key factors in selecting the measurement site.
Wherever possible, the length of the reach should be such that the difference between the water levels at the upstream and downstream ends of the reach is at least 0,25 m.
Flow in the reach should be free from significant tributary inflows (or distributary outflows), and from disturbances in the high-water profile caused by any tributaries or distributaries.
The flow in the channel should be contained within defined boundaries. If possible, reaches in which over-bank flow conditions exist should not be selected. Where this is unavoidable, however, a reach in which there are no very shallow flows over the floodplain should be sought. This will require additional computations for determining the discharge. ISO 1070 pdf download.