Selection and Application of Manning’s Roughness Values in Two-Dimensional Hydraulic Models

Measures to improve the accuracy, reliability, and consistency in selecting roughness values for the application of 2D hydraulic models at highway crossings and in transportation corridors will represent a major step forward in the evolving state of practice. Whether a one-dimensional or a 2D modeling approach is taken, inconsistencies can exist from state to state, and even within states at the various district levels, on how to develop accurate and reliable hydraulic models. The fundamental issue is the selection and assignment of Manning’s roughness values for a variety of channel types and land uses.

NCHRP Research Report 1077: Selection and Application of Manning’s Roughness Values in Two-Dimensional Hydraulic Models, from TRB's National Cooperative Highway Research Program, presents guidelines for the selection and application of Manning’s roughness values for 2D hydraulic models.