A depth indicator is a device used to indicate to drivers the maximum depth of floodwaters across a road. The zero mark on the Depth Indicators is set at the lowest pavement level on the section of road liable to flooding.
Although a depth indicator indicates the maximum depth of water it does not indicate how fast the water is moving or if the road surface under water is still intact and trafficable. The water level may also still be rising. Motorists should generally not attempt to drive through water covering the road.