What effect does a hump on an open channel bed have on water level?

A hump on an open channel bed can alter the flow characteristics significantly. In the case of subcritical flow, which is characterized by a Froude number less than 1, the flow is slower and deeper. As water approaches a hump in such conditions, the water level tends to drop over the peak of the hump. This occurs because the flow must accelerate as it goes over the elevated section, resulting in a localized reduction in water depth at the top of the hump.

The dynamics of fluid flow dictate that as velocity increases, pressure drops, leading to lower water levels at the peak of the hump under subcritical conditions. This principle is rooted in Bernoulli’s equation and the conservation of energy in open channel flow. Hence, when subcritical flow occurs over a hump, there is indeed a decrease in water level at that point due to the increase in flow velocity as it traverses the height of the bump.

In contrast, observing water levels in supercritical flows or at other variations of flow types would yield different interactions with channel geometries, where the principles of energy conservation play out differently. Understanding the relationship of flow types with channel features like humps is crucial in hydraulic engineering and water resource management.