When a natural drainage traps or traps an irrigation channel, it is necessary to construct a suitable structure to safely advance the channel. Because these works are done to pass drainage, they are called cross drainage work. These are also called CD studies.
It should be noted that such additional work in the channel increases the cost of the project. Therefore, such studies should be avoided as much as possible.
It can be obtained in two ways:
First of all, the alignment of the irrigation channel should be changed in order to prevent the transition to the discharge channel.
Second, the drain itself can be directed to the adjacent stream to prevent passage. However, in practice, such a transition may be impossible to avoid. So there is no alternative, to build a structure to move the channel into the channel.
Cross drainage works is characterized as when an irrigation waterway is blocked by a channel which is required to be crossed over the trench, some appropriate structure is required to be developed. Along these lines the designing works developed to cross the trench by the channel is called cross drainage works. These additionally incorporate the crossing of waterways, streams, channels and common water course.
Types of Cross Drainage Works
Following are the different types of cross drainage works which are developed under various condition:
These are much the same as extensions with the exception of that instead of conveying a street or railway over these, they convey trench on the top and drainage is passed under the channel to such an extent that its high flood level (H.F.L) is always lower than the underside of the supporting structure for the waterway. The essential thought in concluding whether ought to be an aqueduct or a siphon aqueduct is the general sizes of channel and the drainage to be crossed. In the event of siphon aqueduct, as the trench bed isn’t clear over the high flood level. The general distinction of levels between the two channels is a lot less and overwhelming banks are for all intents and purposes wiped out. Consequently it tends to be said here that when the drainage is little when contrasted with the trench, guiding of the drainage will for the most part be favored for taking the waterway in high banks. The distinction of bed levels among trench and drainage can be appropriately modified by changing the channel arrangement.
Contingent on the constructional highlights, the aqueduct is of following types:
a) Pipe Aqueduct
At the point when the channel is extremely little, it ignores the channel through the pipe line which is called pipe aqueduct.
b) Irrigation Culvert
Where the width of the channel is from 2.5m to 16m little culverts are given to deplete over which waterway is passed. Channel disregards the culvert.
c) Irrigation Box Culvert
It is likewise called irrigation chunk channel type aqueduct. At the point when the width of the channel is little i.e., up to 3m, the channel might be gone through rectangular passage or a culvert.
d) Siphon Aqueduct
Siphon is the structure where the trench water went through a transformed guide under a drainage. The channel water is permitted to stream under tension when tail water level under a siphon is higher than the under surface of the culvert and elevated pressure is applied on the covering of the roof. To guarantee the wellbeing of the work under most noticeably terrible conditions, it ought to be accepted that there is no water in the channel around then. The inspire pressure at the downstream finish of the barrel roof is equivalent to the contrast between downstream water level and level of the underside of the roof. At some other point along the barrel, the inspire pressure is given by the ordinate between the water powered inclination line and the underside of the roof covering.
2. Supper passage
At the point when the channel is extended the irrigational waterway, the cross drainage is known as a super passage. The channel streams in barrels or passages under environmental tension and don’t run fall and the water contacts the roof of the waterway, the bed of the trench under the channel.
Super passage works precisely like aqueducts and with a similar contrast as in siphon that for this situation the drainage is on top and the waterway is conveyed underneath. As the trench is passed under the drainage, extension ought to be independently developed on the drainage trough to convey the administration street across the drainage. Siphon and super passages are more costly and hard to build and require broad preparing works and an enormous drainage trough to take the high flood release.
3. Level Crossing
At the point when the bed of the waterway and drainage is at the same level a level crossing is given. A departure weir is developed along the channel at upstream intersection. Head of the weir is kept at the full repository level (F.S.L.) of the waterway. At the point when the water level in channels ascends above full store level (F.S.L.) of waterway it spills over the departure weir and blends in with the trench water and is taken out from the channel at downstream intersection by giving controllers.
It is a structure which is given to arrange off overflow water from the supply. Spillway works are wellbeing works for the channel and gives it auxiliary dependability. It likewise passes the rising water level to ascend above high flood level. There are numerous types of spillway, an ogee shaped spillway. The other pieces of spillways are straight drop or free over fall spillway, siphon spillway, entryway spillway, chute spillway, and passage spillway.
To gracefully the water from the supply to the region underneath the channel, outlets are given which are called sluices. Sluices are additionally given to expel the dregs from the repository. They are given entryways which are worked from a stage at the top. Head of stage is kept above full store level (F.S.L,). Another kind of sluices are Belgrain type outlet head divider outlet, Dharwar type outlet and Pipe outlet.