Small Lot Water Retention

1.gravel fill

2.vegetation coverage

3. front yard hosta on red stone mulch

4.pea stone driveway

5.permeable pavement patio old water barrel

7.gravel drip line along garage

I think it is possible to retain almost all of the water that lands on a lot. The biggest benefits come easiest: reduce impermeable paved areas, provide soft areas to absorb rain, store rain on site.

The above photos all come from my 29×100 downtown lot. The lot line is less than 2 feet from the city sidewalk. Photo one shows a retaining wall under the fence at the back lot line, with 3′ of gravel fill in front of it for sharp drainage down into the subsoil. The flagstone path and ground cover let moisture sink in quickly.
I have no lawn, only garden plants. Stepping stones provide access, so the soil never compacts. While grass is OK as an absorbant surface, I prefer perennial plants. If they dont thrive, they dont survive.
My little front yard is 100% planted, and there is a permeable pavement walk to the porch. All the rain from the second floor verandah runs onto the first floor verandah and then into the red stone front garden with its hostas and ferns and japanese lilac tree. This system absorbs 100% of the rain from the verandah roofs and what falls on the garden, including snow melt.
My driveway – picture #4 – is made of 10″ of peastone laid 20 years ago. As fast as it gets rained on, it drains down into the earth. Once a year I loosen the stone with a fork and pick out the grass or other weeds that have moved in.
My patio is made of permeable paving blocks. The joints are quite wide, filled with sand. The whole thing is on a sand bed on top of a gravel base. It is new, and I was anxious to see if I had graded it enough for run off, so twice I have gone out in the midst of those heavy downpours to check on the water. Amazingly, it just runs down into the earth, between the stones. There was no running stream of water downslope to the driveway. BTW, the rubble-stone basement is dry.
I have a single water barrel that fills up very quickly when it rains. I hope to link two more together to retain more water, because I am cheap and that will cut my water and sewer bills. Overflow runs onto another patio, which sometimes puddles in the rain, but it drains down within a half hour or so. None of this water runs overland onto adjacent properties. I have evestrough on one side of my pitched roof, which drains to the flat roof, which drains to the water barrel and patio. The other side of the house pitched roof drips onto my neighbours paved driveway and runs onto his back lawn. Between the pitched roof and the flat roofs, I capture about 60-75% of the roof rain. The flat roofs are slightly concave, and puddle about two inches deep, and drain off slowly after it stops raining, so I can keep 100% of light rains and a bit of heavy rains.
My neighbors garage is shown in picture 7. It is on the lot line. I put recycled red stones (a curbside find) along the garage with landscape fabric under it to control weeds. I take all the rain that lands on the slope that comes towards me and direct it into my periwinkle and lilly beds.
For my flat roofs on the back addition, I have been researching green roof systems suitable for residential installations. I will shortly be building a few shallow boxes/trays for sedums, which I will pop up onto the flat roof to green it and experiment to see if they will retain enough water to survive, since I certainly wont be watering there.
If I can retain a very high percentage of rainfall on my small lot, it should be a lot easier to retain it on larger and suburban lots (lower ratio of building+driveway to vegetated area). Of course, there are other variables, such as subsoil conditions, what is upslope or downslope, and the amount of care the property owner is willing to put in. But the very basics – reducing impermeable surfaces, storing roof runoff, having permeable landscaping – do not require special skills or knowledge and could easily be the “norm” for builders and homeowners alike.

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