water + stormwater
When it comes to developing and executing an effective surface drain- age plan, a number of factors have to be taken into account. The basic purpose of a surface drainage system is to shape and mold the land into a watershed that can convey the runoff into an organized drainage system comprising of catch basins, trench drains, and storm sewers. If your surface drainage is below par, it will have a detrimental impact upon the subsurface drainage. Surface drainage has to do with any manner of regulated removal of surface runoff on account of the spring thaw, irrigation, precipitation, irrigation, or anything else that leads to surface water accumulation. If you don't deal with overflow in time, it will have an adverse impact on the land and surrounding structures. Improper planning may lead to erosion and sedimentation. When one talks about a comprehensive drainage system, surface drainage is at the forefront. A good surface drainage system is the only way to cope with heavy volumes of surface water accumulation after bouts of intense rainfall. Not doing so will quickly saturate and overwhelm the capacity of the soil to absorb wa- ter, which could lead to extensive flooding and changes in landscape structure. Let’s look at what some of the major surface drainage systems are: 1. Open Drains These can be of varying dimensions and are principally of three types: Shallow- These are only up to 0.3 meters deep and can be created with the help of a hand shovel and can help remove water from shallow depressions and direct them to a larger drain or a stream. These are not really suited for draining a large expanse of land and are more in the shape of a temporary arrangement. Medium Depth- Such drains are between 0.3 to a meter deep and are created with the help of an excavator and are typically V-shaped and flat at the bottom and a gradient that is steep enough to help water flow through quickly without damaging the drain walls or bottom. These are best suited for flat areas. Large- Large open drains can be several meters deep and wide and are created with the help of dragline excavators, bulldozers or scrapers and are capable of evacuating large volumes of water. 2. Humps and Hollows This is a system where a surface in question is shaped into parallel humps separated by hollows. This allows the humped shapes to shed Design and Engineering Considerations for Surface Drainage Systems By Ankit Sehgal
excess moisture into the hollows which double up as shallow surface drains. This type of surface drainage is ideal for areas where tile or mole drainage is not possible on account of inadequate depth or fall of the soil. The humps and hollows system creates a series of lateral surface drains that can help discharge water into headland drains. One can use for- mulae to calculate the size of the drain taking into account the amount of water needed to be removed. The spacing between the humps may vary between 10 to 20 meters depending upon the speed with which the water needs to be removed. The greater the space between the humps, the slower will be the rate of discharge of water.
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may 2020
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