A Shiny App for estimating Multiplier Exponent Curves from Manning’s Equation Inputs

(This article was first published on AdventuresInData, and kindly contributed to R-bloggers)

WASP and other flow and water quality models ask users to input multiplier and exponent values relating velocity and depth to discharge. These relationships take the form of V=aQ^b and depth=cQ^d, where the values a, b, c, and d describe the curve that approximates paired points from other sources. When paired field measurements are lacking, Manning’s equation provides an estimate of open channel flow based on channel characteristics.


This app takes Manning’s equation input variables and fits nonlinear least squares parameters to estimate a, b, c, and d over 20 equal increments of depth from 0.05 meters to the user specified maximum. The computations assume a symmetrical trapezoidal channel with continuous sloped sides.

The app is available here including a link to download the code and a separate link to download a batch version of the same tool.