Perhaps this agency directive will help develop a desired rating curves. I suppose if you have an engineered channel, the water level and gradient might be helpful, but normally for each stage measured in a stable cross section, the flow depths and velocities are measured at numerous points using a current meter. A Doppler float is expensive, but can be used to reduce time to take a measurement. Measures are taken at several low, moderate and high flow stages to develop the stage discharge relationship. Due to the long term importance of these sites, a high quality survey of cross section with benchmarks is desired.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=31844.wba

The only velocity tool that involved the us and ds elevation that comes to mind was the velocity head rod. It was less accurate, and used in wading, sometimes hard to read, where the water level jump on the upstream side when the full width of the rod was perpendicular to the velocity, against the water level drop when the head rod narrow side was against the velocity. This tool did not appear reliable because the highest flow velocities are near the surface as compared to standard current meters that are positioned at 0.6 depth, or sometimes other depths in deep waters to get a average velocity reading for that cross section point.

The rating curve is a relation between stage (river level) and streamflow (discharge). Each streaming channel is different and, because the stage-discharge relation is a function of the streambed material and geometry, each rating curve will be unique to that site and a particular period of time.

The rating curve depends on the hydraulic characteristics of the stream channel and floodplain and will vary over time at almost every station. There might be subtle changes to a stream channel, such as the growth of aquatic vegetation in the summer, frequent shifting of a sand-bed stream bottom, catastrophic changes due to floods, or man-made changes such as the construction of a bridge. These changes might require only minor or temporary adjustments to streamflow records, or could require a complete reevaluation of the rating curve.

Rating curves are developed over time. Each time a site is visited, stage and discharge are recorded. After sufficient a sufficient number of stage-discharge pairs are collected and plotted, data are collected, a line (curve) is drawn through the points to describe the relation.

Regards

THIS EQUATION IS KNOWN. WE SEARCH ANEW EQUATIONS TO CONNECT WETH MULTI PARAMETERS

William F. Hansen Thank you for putting that paper on here. I plan to use this protocol to determine the stage-discharge relationship for programming my automated samplers.

This paper is useful for anyone that is setting up water quality collection sites that collect on a flow interval in areas where a flow regulating implement (like a flume or weir) is not possible or would create undesired environmental impacts.

https://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=31844.wba

Kindly check on thus paper

https://www.scirp.org/html/7-9403674_92238.htm

Frankly speaking, I do not understand the question.

What are you looking for?

Rating curve has nothing to do with the u/s and d/s...It is generally curve between the stage (water level) of the river with respect to discharge of the particular cross section.

In order to calculate the discharge further D/s of that we need to evaluate through the flood routing.

Regards

Vikram