rain gardens to reduce flooding

This shows a method of ensuring existing stormwater systems are not flooded in todays world.

Rain gardens are extremely common where I live.  I think most cities require them for new housing complex or road planning over the last 30+ years.  They work a treat for slowing water flow, helping storm drains, and storing the water in the soil to help plants grow in the summer drought (and reduce wildfire risk near houses)

Here's a gateway to some of the plans that work well in our climate.
https://www.crd.ca/environment/stormwater-watersheds-harbours/stormwater/managing-your-rainwater

I'm always surprised they aren't more common elsewhere.  

R Ransom, that link was a good one.
Interesting topics, but they speak of storing rainwater in small containers not large 5000gallon ones.
Is that some sort of cultural thing because so many areas do the same?

A school in Santa Fe, New Mexico, has done a 7 year research study on the efficacy of various parking lot run-off options. The identified goal was to determine if even in their dry environment, could they plant and grow trees with *no* supplement irrigation by using curb cut/rain garden water collection only. Even in their dry environment, their efforts were successful.

This relatively inexpensive research program, collected data about how deep the water infiltrated when held just long enough to soak in. No standing water to risk mosquito issues, but also, minimizing water overflowing beyond the treatment area.



The following link is to the actual research paper for all the numbers and diagrams included.
https://www.westernplanner.org/2022/2022/10/22/green-stormwater-infrastructure-in-a-semi-arid-climate-the-influence-of-rain-gardens-on-soil-moisture-over-seven-years

I live where this happens almost every year in July.

Maybe rain gardens might help though I don't see this as ending flood water just decreasing somewhat.

The is just too much water when the creek rises 13 feet as it did this year.

Anne, when a river rises so much more than usual, reasons possible are;
- the issue of changes to the upstream landscape that has increased runoff.
IE forest replaced bt pasture, pasture now recently tilled soil
- higher rainfall.
- river improvements including removal of snags, blockages etc.

John C Daley wrote:...
- the issue of changes to the upstream landscape that has increased runoff.

The biggest issue in my area is the increase in "hardscape" by humans.
1. Houses are much larger and cover more of the property.
2. Gravel driveways being replaced with asphalt or concrete.
3. "Wild" hedgerows being replaced with monoculture hedges, or worse, grass.

Yes, the storms are getting larger and wilder. However a fairly bad storm went through Geoff Lawton's farm in Australia. He had almost no damage, and the damage that was done was easily repairable, because he'd done the permaculture approach in advance.

If we get everyone in increasingly risky areas, getting everyone in the landscape to take a more permaculture approach, we likely could reduce the levels of damage we're seeing from storms in many cases, even if not in all cases.

John C Daley wrote:R Ransom, that link was a good one.
Interesting topics, but they speak of storing rainwater in small containers not large 5000gallon ones.
Is that some sort of cultural thing because so many areas do the same?

That site designed for urban and suburban (aka, lots 1/32nd of an acre or smaller) and city planners where the flooding risk is greater due to the ratio of road and driveway to nature.  A rain garden looks better and holds far more water. It adds greenspace whereas a big water storage tank, takes it away.  A water garden can even be in a tiny space like the bit between the sidewalk and the road, or between lanes.

Our tanks are more farming rain water tanks, but can't remember the size, about 8 to 10 foot across and 6 foot tall.  The number had a lot of zeros for how many liters.  Basically, it's bigger than most tiny houses.  This usually fills up in 3 days of our rainy season.  The other 5 months of rainy season, the water is wasted.  Even the ones that are taller than I, fill in about a week.

I've never seen a rain garden fill up (as the build them here - but the cities has something like 50 years expired building them for our climate).  It slows the rain, holds what it needs to keep growing green.  The goals in the city are to look good without irrigation (we have water bans in the summer), reduce pressure on storm sewer.  But from small experiments on the farm, I think the same technology can be used in much bigger ways.

John, my creek has a seven mile long watershed upstream. It used to have a stable bed... established tuft grass in wide parts of the bed,  flat stones a century old shingling the spot where a gas pipeline used to run across the creek. Then in 1972, an interstate highway was built across the headwaters with fast drainage into the streambed and remnants of Hurricane Agnes caused major flooding in the region and uprooted all established natural stable features. The features never returned, and floods now erode every year. The remnant pipes dangle 4-6 feet in the air, and the bed is eroded down to bedrock in that spot. It will probably be a century or two before the bed stabilizes again starting from that bedrock area just upstream of my land.

Glenn Herbert wrote:...Then in 1972, an interstate highway was built across the headwaters with fast drainage...
It will probably be a century or two before the bed stabilizes again starting from that bedrock area just upstream of my land.

Unless humans intervene and build Beaver dam analogues and hey... maybe even allow Beavers to return.

A huge part of the hydrology of both Europe and North America was created and managed by Beavers. Now humans need to do the Beavers work!

Just think of how this could have been different if the highway had been built with a series of rain gardens like a string of pearls along its edge instead of assuming a creek could take all that fast runoff? We'd have tall trees by now that would have helped clean the air and break up the noise from the vehicles. A gal can dream, can't I?

Glen, that is an interesting story about the pipeline and the road.
As a Civil Engineer I would like to study that issue, can you give me more details please?

I have no real information on the pipeline except that there was an easement in the deed from late 19th-early 20th century. It was abandoned long before my parents bought the land in the mid 50's, though they didn't bother to remove the pipes crossing the creek.

The highway was Interstate 88 which runs between Binghamton and Albany in New York State, and you can probably look up information about it.

There was once a beaver dam on a wide flat part of the creek upstream of our property for maybe a few years, and a beaver lived in our pond formed by a concrete-faced dam for a year or two, but the creekbed's grade is too steep at least in its lower half for any beaver dam to survive a common flood, when the water can rise 3 or 4 feet in a few hours.

Jay Angler wrote:

John C Daley wrote:...
- the issue of changes to the upstream landscape that has increased runoff.

The biggest issue in my area is the increase in "hardscape" by humans.
1. Houses are much larger and cover more of the property.
2. Gravel driveways being replaced with asphalt or concrete.
3. "Wild" hedgerows being replaced with monoculture hedges, or worse, grass.

Yes, the storms are getting larger and wilder. However a fairly bad storm went through Geoff Lawton's farm in Australia. He had almost no damage, and the damage that was done was easily repairable, because he'd done the permaculture approach in advance.

If we get everyone in increasingly risky areas, getting everyone in the landscape to take a more permaculture approach, we likely could reduce the levels of damage we're seeing from storms in many cases, even if not in all cases.

I've just begun studying in a master rain gardener class in my community. I realized that it takes a much smaller area than most people probably think to capture a fair amount of what would otherwise runoff and give it time to soak in.
A lot of suburban communities, even in the dreaded HOA holes, could find ways to use small areas to manage each home's water runoff, but the suggestion of permaculture sends people running clutching their pearls like someone suggested adding portals to hell in their front yards.  Yet there is increasing acceptance of terms like rain garden, so I am hoping to bring permaculture awareness in bits and pieces to the suburban masses. If they won't buy in under one word I'll sell them on another.

Some of the raingardens are tiny, about the same footprint as one of those small rain barrels on the surface.  But they have a huge impact on waterflow.

I like the ones between the sidewalk and the road.  They are maybe 10 foot by 2 foot.  They take the runoff from urban rain and keep it off the road.

But the technology has a lot of potential to scale up.  Something like burm techniques or other earthworks.