Project: Extreme Water Runoff
A very difficult project because of four lots above and a long paved road that all dumped stormwater runoff onto the site. Complicating this was the fact that the concrete driveway also fed into a one-foot area three feet from the house, cutting the property in half, separating it from its yard. We had to divert the huge volume of rain runoff 90° and tie it into the culvert.
Over 400 feet of stone was laid into a channel and two stone collection ponds were added. No liners or mortar was used, so the entire dry stream irrigates the fruit trees and flowering bushes and border plantings that stabilize the banks. Sure, rain barrels are good — but this saves all the watering time.
These "before-and-after" photos show how you can keep a dry property watered during frequent droughts (remember those?) yet also capture the biggest rains. They follow the path of stormwater runoff from the highest point of this steep-slope property to the lowest. Accompanying each before-and-after pair is a map, based on the animated graphic at left, that shows you which section of the runoff-control system you are viewing.
An aerial shot shortly after installation of the stormwater-runoff system in 2005. The house is below the paved road and below the lot to the left, and also receives the runoff from a number of houses across the road through a 24" culvert. Great!!! More water = more plant growth — if we can keep it on the property.
The animation shows the path stormwater runoff follows from the highest point on the lot to the lowest. The orange raindrops show the path it was taking before the channel was installed, traveling destructively down the steepest slope into a mountain stream. The blue raindrops show the slow, winding path it takes now — nearly double the previous distance — maximizing the ability of the property's permeable surfaces to absorb it.
Roll your mouse over each "after" photo to see how attractively each section had grown in a year later —
and how effectively the system handled the most extreme stormwater runoff in 2009 (see 6. through 9.).
is a view looking due east up the road with your back to the lamppost and driveway. The water was coming down the road in sheets and dumping towards the house. The erosion channels it was carving can easily be seen.
The row of green dots on the map above
are the 6-ft. evergreens at right
. We ringed each one with stone 280°, leaving them open facing uphill. The top of the road would be sodded and seeded and would accomodate 10 cars of overflow parking, as shown in the view at right
(looking due west this time).
, the phone box and even light pole were sliding downhill, but this water flow could feed a row or two of privacy evergreens before being funneled around the transformer into another garden, right
. We needed to keep the transformer bed from eroding while planting it to disappear.
By guiding the water around the wall (right
) instead of against it (left
), even in the biggest storms we were able to stop the erosion. By having it fill the planting beds before overflowing across the driveway, we added another 65 ft. of watercourse.
The 100-ft.+ concrete driveway — including all the water from above it — all funneled to a point in the center of the photo at left
, the stone pavers on right of the photo are the original path of the runoff. The rip-rap dry stream (see 5., below at left
) was no match for the steepness, and so the water often jumped the stream bed and ran across the small lawn and straight into the stream. The waterway bending to the left of the pavers now catches all of it.
The original rip-rap dry stream bisecting the yard from the house is shown at left
, and as an orange line on the map above
, the turn the water now makes as it meanders across the hillside before joining with the culvert runoff.
A 24-inch culvert (at left
, center distance) carries runoff from the houses across the road.
, the waterway along the hillside joins with the culvert under the road. As the map above
illustrates, the force of the water pouring out of the culvert strikes the stream coming from the hillside waterway like a billiard ball and turns it at a sharp angle, keeping the water flow inside the property's boundary.
, the culvert before simply spilled out onto the ground. Note road at above left.
, the dry stream into which the culvert now empties runs along the boundary line in front of two rows of border evergreens and a fence of rhododendron limbs for privacy.
In this relatively flat area (left
) we put two collection pools, shown at right
. The first pool, on left of photo, is thigh deep. The second pool, to right and below, is shin deep. Check out the picture of the professors standing in between them, at 11. below
, the site of the lower collection pool before.
The pool's stones (at right
) are over 4" thick, so they catch a lot of sediment (keeping it out of the creek) and withstand a lot of current.
The creek area at the bottom of the property before, at left
After, at right
, looking upstream toward a natural waterfall. The photo one year later
shows a rock bench and the path to a fire pit and seating area.
Shortly after completion, the stormwater system was inspected by Henderson County watershed-restoration expert Diane Silver
who dubbed Steve the "extreme-runoff guy." Following up 3 1/2 years later, three state
erosion-control experts from the North Carolina Cooperative Extension Service of NC State
University inspected it for educational purposes. Here they are shown at the rim of the largest catchbasin. From left to right:
, Assistant Professor and Nursery Extension Specialist;
, Extension Area Agent for Henderson/Transylvania
, Extension Agent and Interim Director for Buncombe