Swaling on chalk hillside

We're about to begin an ambitious 3 acre permaculture project on the sussex downs. One problem I'd like some advice on is the swaling. The ground has only six inches of topsoil over a chalk substrate (common to the South downs) Water therefore moves rapidly through the soil and is lost. What would the best swaling tactics be here - a hay/straw filled trench type swale, feeding run off ponds?

Bulding the berm downhill from each swale around a core of conifer slash would probably help a lot. The buried wood and green material will decompose, helping to neutralize the chalk and also retaining water and nutrients. Even hardwood would help to make a neutral soil, but I've read that conifers are more acidic; they might also be more abundant. See the article and/or forum thread on hugelkultur for more details.

I wonder if a pond liner could be made from local materials. If you can find some mix of chalk pebbles and dust with fine silt that holds together reasonably well, in principle I think it might be sealed with water glass, and then another layer applied over it to protect that waterproofing.

This is great stuff - thanks a lot for the advice. Am going to try exactly this, and see what local sources of conifer I can find. Will check our hugelkultur as well, which I know of in principle, and have tried on a small scale.

As for the pond liner, that is fantastic. I've been reluctant to embrace the idea of importing a bought pond liner of doubtful ecological footprint. Lots of food for thought here. I'll post my findings on the forum as the project happens.

The bare ground from earthwork gives you an opportunity to modify flora.  With the mix of calcium rich parent material and humid well drained, what is your soil pH like?!  What kind of mineral deficiencies do you tend towards?

I bet the kinds of plants you'd want to break up and mine the chalk are in the native flora...  Have you ever poked around in the ecological flora of the british isles.  You have a couple hundred years of vegetation ecology headstart.

I think Hollingsworth is pointing you in the right direction with wood as a way of storing nutrients and moisture.

I would also consider a rapidly growing, chalk tolerant, nitrogen fixer a critical component to go with the wood.

That sounds ideal Paul and thanks! - any recommendations on the right nitrogen fixer?

Don't know a thing about chalk downs or England... Around here I grow clover, alder, and lupine, black locust, goumi.  I was figuring your local flora would point the way, and the question about pH has something to do with what species thrive.

there isnot much problem abotu keepign things wet in the south downs is there? I thik swales are a way of helping in dry areas. THey say south facing slopes get dry.
  Swales are also a way of stopping flsh flooding. agri rose macaskie.