Landscape Architecture Resource

Yes, I have to look it up from time to time myself. If you haven't done any grading in the last year or two, you can get a bit rusty.

Slope = Rise / Run

or

Slope = (Difference in Elevation between two points) / (horizontal distance between two points)

or

S = D.E. / L
where S = slope as a percentage
D.E. = Difference in Elevation
L = Length

These are just three ways to say that a 5% slope means that the ground rises 50mm over a run of 1m.

Personally I think grading is a lot of fun. I've always enjoyed solving math problems, maybe I'm a grading geek then. Grading is like a series of very easy little math problems done graphically. It's like drawing, but it feels more like sculpture to me because you're really drawing in 3D as you note elevations on your plan.

I'm always disappointed when a civil engineer has made it their job to do the grading for a site. Usually the landscape architect will work out the finer details, even if the grading has already been done by a civil engineer. With all due respect, if you leave the landscape grading up to the engineers you are likely to end up with something after construction that looks... well, engineered.

Sometimes hard angular engineered slopes is the look you are going for, but usually we want landscapes to flow, feel organic and natural, or just plain look attractive. Sometimes, as in the case of wetland design, there are ecological considerations that the civil engineer may not be aware of. Altering slopes can make a huge difference when you are talking about tree irrigation, planter drainage, views from the playground or bus-stop, or stream-bank habitat.

And yes, landscape architects are experts at stormwater management and drainage. So just because you end up with a site that looks beautiful, don't think it won't function just as well as something an engineer may draw up. It may even function better. Appearance isn't everything, but when all is said and done no one ever thinks about all the lines and pipes below ground. It's the actual human living space on the surface that people experience. So the whole process should ideally be driven by landscape architects, with the engineers filling in to stamp their expertise where necessary.