Civil Engineering - Irrigation - Discussion

Top bank-level means (TBL) normally all the sections are designed by FSD level. Full supply level or depth. But in case of emergency water supply or rainy season free board is required. TBL also called berm level or key level is the top of the canal.

A berm is a raised bank or ridge that can be used to direct the flow of water through ponds, wetlands, or slopes1.

A freeboard is the vertical distance between the water surface and the top of the lowest bank of channel 2. It is provided to prevent waves or fluctuations in the water surface from overtopping the banks2.

The height of a bank is the vertical distance between the bottom and the top of a bank. It depends on the soil characteristics, hydraulic gradient, and saturation line2.

What is a berm? Please explain it.

Generally, the freeboard is the distance between top-level and supply level which is used in the emergency period. The value is generally taken 0.5.

Freeboard is the distance between the spill way and the crest of a dam.

It is the distance between the full supply level and the top of the bank. The amount of freeboard varies from 0.6 to 0.75m.

@Netai Shil.

Weir is a structure built across a river to raise the water level in the river.

Whereas a bridge is a structure which is built above the river for easy access to the other side.

What is the Difference between weir and bridge?

It is provided to safeguard the structure doing emergency period.

Free-board is used to control the overflow in high rainfall period.