Establish Effective Lower Bounds of Watershed Slope for Traditional Hydrologic Methods
Equations to estimate timing parameters for a watershed contain watershed slope as a principal parameter and estimates are usually inversely proportional to topographic slope. Hence as slope vanishes, the estimates approach infinity. The research identified, from literature, data, modeling, and physical experiments, the dimensionless topographic slope where "low-slope" behavior should be assumed. Alternate timing equations based from parametric studies using the Diffusion Hydrodynamic Model (DHM) were developed. A slope-offset approach was explored and is suggested as an adaptation of current technology. The offset value suggested is 0.0005 and an illustrative example is presented in this report. The dimensionless slope suggested for consideration of alternate approaches is 0.003. The researchers found that current streamgaging techniques are not well suited to low-slope hydrologic studies and different measuring methods are suggested.