open levee; discontinuous levee
A levee with intentional gaps to allow floodwater to flow back into the river channel after a flood, reducing pressure on the levee system. Technical term in civil engineering.
Open levees serve to temporarily divert floodwater into retarding basins during floods.
Compound of 霞 (かすみ, 'haze' or 'mist') and 堤 (てい, 'levee' or 'embankment'). The name likely derives from the way the discontinuous levee segments appear to fade in and out like mist when viewed from a distance, though the exact origin is uncertain.