Document Type

Article

Publication Date

2024

DOI

10.1119/5.0167974

Publication Title

The Physics Teacher

Volume

62

Issue

4

Pages

A317

Abstract

On a hot afternoon in western North Carolina, the heavens opened and (to mix metaphors) it started raining “cats and dogs.” The rain was torrential, and soon a river of water was flowing downhill into the parking lot. In rivers and dam spillways, these are known as flood waves. The picture shows a particular type of flood waves known s roll waves—shock-like patterns separated by smooth profiles. In a steady-state situation, the drag forces on the water in the channel are balanced by the down-slope gravitational force. The dimensionless friction coefficient is C, the stream depth is h, v is the average speed of the water, g is the gravitational acceleration, and α is the angle of the slope (assumed to be small so that sin α ≈ α). In a steady state, Cv² = ghα.

Rights

© Copyright 2026 AIP Publishing LLC.

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in

Adam, J. (2024). Cats, dogs, and roll waves: Solutions for Fermi questions, April 2024. The Physics Teacher, 62(4), A317.

and may be found at https://doi.org/10.1119/5.0167974

Original Publication Citation

Adam, J. (2024). Cats, dogs, and roll waves: Solutions for Fermi questions, April 2024. The Physics Teacher, 62(4), A317. https://doi.org/10.1119/5.0167974

ORCID

0000-0001-5537-2889 (Adam)

Download

Share

COinS