ABSTRACT
The afflux or ponding back (A*) caused by the constriction is relatively
small, and this is a considerable asset when the fall available is strictly limited, such as for example on irrigation canals in flat country. Other favourable characteristics are robustness of construction and a relatively clear passage for the water. Maintenance is simplified, since floating debris and suspended matter are unlikely to cause damage or be de posited; also, only limited protection against scour is required as the regime of flow is not greatly disturbed.
