Trenches were generally dug with a sump about two foot deeper than the intended depth of the trench. this was then covered with 'duckboards' essentially any old timber that was nailed together to be easily repaired, allow quick drainage & study enough to survive the tread of countless feet.

Dug outs (bunkers dug deep below the surface) often contained a sump, but bigger ones were provided with electrical generators and pumps to prevent them filling with water.

In some areas the water table was too high to allow digging, and consequently large sandbagged ramparts were created about ground.

All of this required constant maintenance by works parties while troops occupied the trenches- ensuring pumps were well maintained, the sump didn't collapse as well as revetting trenches (the metal and wood stopped the trenches from falling in on themselves). if these method failed then troops were expected to bail out their trenches as best as they could. This maintenance increased during period of heavy rain, and on some occasional trenches completely collapsed, necessitating withdrawal.