Q. Explain the Design of waterway?

When the river flows between high banks and the whole width is actively functioning during high floods, the bridge waterway should practically be equal to the spread between stable banks at the design flood level. This practice may be followed even if such a river slightly overtops the banks during extraordinary floods. These conditions may normally be met with in incised rivers and in upland reaches in river gorges.

If in the above type of rivers, depth of spill is appreciable, waterway should be suitably increased beyond bank to bank width in order to carry spill discharge without causing afflux beyond permissible limit.