These waterways are called grassed waterways, sod waterways, or meadow strips, depending upon the nature of the protective material planted to create the desired roughness. These waterways are constructed along the slope and have protective embankments on both sides to contain the runoff. The capacity of waterways is designed on the basis of expected runoff rate and amount. Structures to dissipate runoff energy Drop structures and other engineering devices are installed to dissipate the energy of concentrated runoff, flood water, or flows of long duration. There are several permanent structures usually made from concrete.
Drop structures are generally effective when installed as a pair.
Drop structures can also fail if the anchoring wall and toe wall crumble from water washing away the soil, undercutting, and scurrying. These are specially designed spillways that collect flow at one elevation and discharge it down a slope at a lower elevation. The shape of the inlet and outlet is important to stabilize the chutes and prevent failure. Some energy-dissipating structures are necessary at the outlet of the chutes. A box-like device filled with stone is generally suitable for most conditions.