Lots of water - Draining a steep spring fed slope

[Maf]

Firstly, congratulations on a most informative web site. I'm suprized you have time to get any 'proper' work done with all the emails you reply to !

Please excuse my lengthy site description !

I have recently bought a old house near Grassington, North Yorks near the bottom of the huge Greenhow hill.

The top of the dale is limestone, full of caves and mines but my plot (about 1 acre) is shaley clay with large gritstone bolders. Some spots you can't get a spade to bite and others you can dig through feet of heavy clay only to find a huge bolder with water running beneath.

We had a fresh water borehole dug recently and they had clay down to 9 meters, the house just down the hill has 30 meters!!
The plot slopes top to bottom and right to left such that the back of the house is one and a half stories higher than the front !

Added to this the plot is crossed by a dike some seven feet high under which a large overflow pipe from Grimwith reservoir runs. The higher ground beyond the dike is flatter but below falls around 20 degrees
The site is dotted with numerous springs most of which dry to a trickle in high summer but run like mountain streams in winter surfacing where ever a large boulder breaks the clay.

The principle spring at the top of the garden flows into an old field drain two foot wide, one deep lined with stone and flagged on top. This passes through a foot wide pipe under the dyke that the reservoir engineers put in.
It fails to cope when it rains hard or snow thaws quickly. As such the shored up land above the dike has gradually slipped through the drain creating a sedge filled pond-like crater !

Below the outfall from the dike is a marshy area at the head of a gully that cuts to about eight foot deep at the bottom of the plot !

Of course I bought this house for a gardening challenge but didn't realize the shear quantity of water flowing through.

This situation will be worse next year as I've put in a trench to take the spring directly above the house to the gully, installed previously non-exisitant gutters and downpipes that also dump into it, lets not mention the driveway to the front that was previously draining into the below road-level kitchen.. In short lots of water !!

My garden plan was to make the gully into a feature by creating a series of pools staggered down the slope, but seeing the flow of water in winter (dunno the rate but think of a one and a half foot channel on a 20 degree slope at one foot deep?! I'm not too sure. All my plants would be washed away!

My idea is to place a big (but How Big) perforated drain along the length of the gully, cover with rubble and use liners to create my pools. Question is how do I ensure that the pipe is big enough so not to bubble the liners or cause my dams to break ? A friend of mine suggested that I should ram some steel girders into the ground to support any significant dams (but failed to quantify 'significant')

Then there's the question of creating a lawn, could I lay gravel then topsoil and turf or would the topsoil just dissapear into the gravel and the turf bake in summer?

Who sells big Perf Pipe ?

Any ideas

Cheers

Mat

[Tony McC]

You really need an on-site evaluation to come up with a viable solution to all those challenges, but it's not insurmountable. A 450mm dia perforated collector drain should cope, even with the winter flow, so it's just a matter of how to conceal such a pipe.

You can buy that size, and bigger, via firms such as UGS, Cooper Clarke, Burdens etc.