Is the garden or restoration in a snowy area?
Is the snow in a loose form or compressed form? A covering of ice or
compacted snow is especially dangerous for herbaceous plants and
prostrate woody plants. ... “respiratory carbon dioxide attains
concentrations as high as 44% and oxygen drops to 3-5%. Under such
conditions [it is] comparable to flooding-induced hypoxia” (Sakai). If you have a spot where the snow
slides down a roof or accumulates in deep drifts this is why the plants
look drowned when the snow melts; a funny form of poor drainage.
the worst case. If once in the last 50 years this site had 50 inches of
rain, plan on it hitting your installation the next rainy season (maybe
the next day). Work out the square footage of your site and how many
actual gallons are going to go through the drain. Knowing if it is
10,000 or 1000 is very helpful. If you have a 3000 sq. ft. roof and a 2
inch downpour a 3 inch drain probably will not work! Four inch drain
pipe is pretty much the minimum for residential installations. A solid
PVC, non-perforated leach pipe is preferred over corrugated pipe. After
a few years, four inch, smooth-walled PVC pipe will carry almost as
much as a six- inch corrugated pipe. The smaller, three inch corrugated
'drainage' pipe is a waste of time and money. If silt drains off the
site, the pipe will silt up in one year.
If you are working in an area where native
plants are about, look them up on our website.
If they live in riparian, freshwater marsh or meadow plant community,
the area is a wet spot most years, and flooded on bad years. If you've
something on a site as the water source that created this wetland,
figure out what it is and how to work with it to control the wetland.
Diversion walls only work on surface drainage.
Burying a wall 6' deep to divert a spring just doesn't work.
Usually sub-surface water is more difficult
than the surface water. Put French drains in against walls or
foundations that act as dams or catch basins, and use this water in a
spot where you need seasonal water. Alternatively, plant these
poor-draining spots with reeds and rushes that have internal aeration
systems so they can live in bogs. Lowering the grade and moving dirt
around so the sub-surface water becomes surface drainage is often more