Rain Gardens

Holistic Analysis

Having installed several rain gardens large and small and also having been present when they got really popular in the states, these are simple design features which preform many functions.  And I can’t bring you any further in amollison description of this design element until Uncle Bill and his great quote is heard which exemplify rain gardens,

“Though the problems of the world are increasingly complex, the solutions remain embarrassingly simple.”

We have crumbling infrastructure in cities, flood and drought syndrome costs are far reaching and expanding deeper into the social realm, water quality degradation rages on, CombineWasteWaterOverflowand water shortages are becoming commonplace in headlines.  These are increasingly complex problems that are usually followed with high energy (high monetary investment) solutions which  merely bandaid the problem.  Storm water runoff surges damage municipal pipe infrastructure. Meanwhile because the storm pipes are most commonly combined with sewage pipes, raw sewage bypasses treatment plants in times of heavy rain causing water quality challenges. This problem/opportunity must be examined systematically and holistically rather than materialistically and rationally as done currently by governments and developers. In other words, where are the leverage points, where is the point source, and how can it be managed to be seen as a resource instead of an extra cost?  A good framework might be to answer the following questions:

  • How does the rainwater off roofs help to grow food locally and abundantly?
  • How does it support native species and biodiversity?
  • How can we examine the “phrase from roof to river” to maximize the resource and give back at the same time?
  • What costs are associated with floods, droughts, and combined piping in municipalities?

Our ethics in permaculture look for integrated, simple solutions and the principles lead us to the design for interconnectedness.

us-rivers

The General Pattern

The phrase roof to river is indeed a great lead into justify why to install rain gardens. Roofs or roads, sidewalks and parking lots, compacted lawns and patios being the headwaters and a base point for the observation and assessment part of the design process.  The source we examine is a surface that is referred to as impervious and sheds water at different flow rates.  The assessment phase of the design process can be aided by our page on catchment calculations as it details flow rates and aids in calculations pertaining to how to size the earthwork appropriately in relation to the catchment area.  Most often with rain gardens the surface that feeds the earthwork is a roof and is accompanied by gutters and piping. These facilitate distribution to certain points and when possible it should be directed into a water harvesting earthwork instead of a sewer system or carelessly cascading through the landscape. Furthermore, the rain garden itself in its easiest definition is the following, “well, it’s a hole in the ground with some mulch and some flood and drought hardy plants.”

Rain Garden Schematic

Rain Garden Schematic

When presenting this topic in a weekend PDC in Cincinnati, Ohio, USA in 2011, I was asked where in nature this occurs since I was speaking about how we get inspiration from nature.  The next day I went for a hike and found the inspiration before me.  It was a fallen tree, very recent, that had lifted its root ball which had quickly accumulated organic material and rainwater.  The picture below is from this event and I of course documented it and reported back to the student the next week my observation.

rain garden inspirationBy comprehending and copying, as Viktor Schauberger would say, ecosystem services are accomplished with little input. So in the context of a rain garden the water is directed towards a basin that is sized to the roof catchment area and abundant rainfall amounts.  Volume holding capacity of the earthwork should correspond to volumes of water being shed by the impervious surface under high or regular rainfall amounts.  You can always over or under size but the plantings may suffer and a planned overflow is always necessary.  Earthworks should be located 15 ft (4 meters) away from the house to protect foundations. Remember rain gardens, like swales, are meant to infiltrate not store water so they are uncompacted and should drain within 24 hours.

The process:

The size, shape and volume of the basin vary but rain gardens are generally located on slopes that are very gentle or flat.  Swales essentially are rain gardens elongated but done

Rain Garden at a school in Cincinnati- design and implementation from a local non-profit, the Mill Creek Watershed Council

Rain Garden at a school in Cincinnati- design and implementation from a local non-profit, the Mill Creek Watershed Council

on slightly steeper slopes. Terraces are  implemented on the next degree of steepness. All facilitate infiltration and completion of the hydrological cycle. When on a slight slope the earthwork has a terracing affect so that volume of water can be achieved.  Basically it is a round, or oval shape, or even butterfly shape to increase edge and access.  Tools that aid are shovels, picks, water levels, and wheel barrows.  Machines can be used for the excavation part and in Iowa, USA in heavy clay soils a subsoil ripper is used in larger rain gardens for commercial sized roofs.  Sand was also integrated in these heavy clay situations to increase the earthworks infiltration rate.  Addition of organic matter (compost) also helps to increase the infiltration rate and capacity to retain moisture for the associated plantings.  The basin itself can be coated with compost to help repair the disturbed soil food web from the digging.  Meanwhile the basin is filled with organic material like wood chips or other woody or carbonaceous debris after the basic plantings happen. Plantings on the rim of the basin are also composted and mulched and the rain garden should be designed for access and how it interrelates with other elements in the system.

As the soils and plantings mature, the infiltration rate increases although earthworks do also tend to silt up overtime thus reducing the volume they can handle. The plantings that Untitled1happen in the basin are plants that can handle continual inundation but also periods of dry.  In more humid, temperate climates these are usually prairie plants and nurseries can outfit you with those.  These prairie plants can be part of your integrated pest management strategy. In temperate regions the rim plantings are often food producers with a focus on natives.  In my home region of Ohio, USA plants I suggest on the rim include Chokeberry (Aronia melancarpa), elderberry (Sambucus canadensis), currants (Ribes sp.) and Paw Paw (Asimina triloba).  All are natives and can be a part of a more extensive food forest.  Guilds can be established on the rim with supportive plantings of comfrey, yarrow, goat’s rue, and french sorrel.

paw paw immature fruit

paw paw immature fruit

Project Example:

The pictures below are from a project implementation of rain gardens that are fed by a nearby roof to create zones of humidity in an emerging food forest that I led in early 2013.  In this subtropical Dominican Republic mountain zone of Jarabacoa, these Slide028earthworks ensure detrimental runoff doesn’t happen from the impervious surface.  Instead it supports part of the edible landscaping portion of a farm-to-table project.  They were dug with machines and we used a bunyip or water level to ensure the bottoms were level which was aided by hand digging.  The rims were mulched heavily and planted mainly with Platano’s, a starchy staple similar to banana that the restaurant used heavily.  In between the basins were other food forest plantings and of course the associated support species including nitrogen fixers. The basins were similar to banana circles which have been known to be used as greywater pits and/ or rain gardens in the tropical context.

Large Scale – Infiltration pits

On larger scales, these rain gardens are called infiltration pits or bio-swales.  And if you dig a pond and it receives runoff but the pond is not sealed, it becomes a rain garden.  Giving water a place to infiltrate and interact with carbon and a microorganism filter is extremely important for ensuring that groundwater supplies are kept plentiful and clean.

In my travels to Asia in 2009, I began in Auroville, India in southern province of Tamil Nadu.  This region is a wet/dry monsoon region but a very brittle climate as its abundant rainfall is limited to only two short rainy seasons lasting 8-10 weeks in total.  As climate change is expressed through varying hydrologicial cycles, these regions are facing even more sporadic and extreme rainfall events especially with overexploitation of local natural resources.  In general the brittleness is leading to the land breaking better known as desertification.  I saw plenty of this in the surrounding areas of Auroville but for sure not at Sadhana Forest, a project in the outer zones of the radiating city plan that calls for forestry.  Indeed a forest was grown, a “forest that grows people”.  It all hinges upon the work that the pioneers there did with swales formed into bunds (compacted swales) and also large infiltration pits at the bottom of the land where water was naturally being funneled.  At first glance this would have looked like a pond construction but the bottom was uncompacted and the pebble laden soils didn’t hold water there.  Instead these large earthworks infiltrated huge volumes of water.

These Earthworks transformed what co-founder of Sadhana Forest Aviram Rozim described as “a moonscape”, not a single blade of grass, with the only life seeming to be the cobra’s that would slither through on occasion.  Once the water was put in the ground, a jungle of non-native acacia trees sprung out of the ground as if the water infiltration was a magic wand, an equal and opposite reaction.  A reaction of positivity and regeneration in this case and the project was extremely inspirational as also the nearly 70,000 native trees that they planted of the local threatened ecosystem took more easily.  The support of the “invasive” nitrogen fixers helped to modify the climate and acted as a buffer to the cyclonic storms in which that particular ecosystem entails.  With the trees growing rapidly, with water harvesting measures in place and extending, the groundwater level had been drastically raised.  And not just on their property but surrounding wells also.  And with all of this growth of the land regenerating it seemed to permeate into the travelers who came to volunteer. This shows how the ethics of permaculture become an intertwining mandala and cause ripple effects beyond just countable numbers of trees planted.

Community Meal outdoors under the trees that sprouted and supported from the earthworks

Community Meal outdoors under the trees that sprouted and supported from the earthworks

Written by Doug Crouch

Header Art Bonita Edwards

earthworks

10 Responses to Rain Gardens

  1. Pingback: Rain Gardens | A Permaculture Design Course Handbook | TreeYo Permaculture

  2. Pingback: Rain Gardens | A Permaculture Design Course Handbook | A Permaculture Design Course Handbook

  3. paul taylor says:

    “Though the problems of the world are increasingly complex, the solutions remain embarrassingly simple.” This basically says it all, yet we spend more and more money on ‘studies’ and almost nothing on solutions, we spend vast amounts on cars and roads, but almost nothing on regeneration, eco systems and environment. It was not that long ago that it was a bit of an embarrassment not to have a veggie garden and a few backyard chickens, but now we have made ‘progress’ and it has become almost an embarrassment to have a veggie garden as many housing developments actually ban a veggie garden as a replacement for a front lawn. We need to make the leap from consumers to creators so we can leave something of significance for the generations to come. thanks: paul taylor trust nature

  4. Christopher says:

    Well said Paul. Governments and especially local governments need to have somebody on board to recognise this and advise. The problem is I think the majority of people only want everything to look perfect along with the fact most don’t seem to have time to establish gardens etc.. This generation has moved away from being self supportive which is a shame as future generations won’t have the knowledge that should have been passed on. It is inspiring to see that the permaculture movement is making way with those young people who are following it. It would be lovely if it could be a mandatory course in our education systems!

    • cdoug_e says:

      I agree it needs to be in our school system. I am working on a series of tools that will be the primary teaching tools as well as supplementary ones when we start to get this in high schools and more universities. I taught the pdc at the university level and pushed to have it be a mandatory course for everyone in the university. one day!

      • Rick Hall says:

        Earth Partnership is doing something like this already, building a nationwide network of organizations and schools implementing EP ecological restoration curricular materials as a context for environmental learning across discipline, age, learning style, culture and place. Educators, students and citizen volunteers learn behaviors and skills needed to restore habitat and enact sustainability plans that protect their community’s water resources. Colaboración Ambiental: Latino Earth Partnership is being developed with UW-Madison Arboretum, Institute for Global Health and partners in the Midwest, Florida, Puerto Rico, Nicaragua and the Dominican Republic. We are headed to work with the Environmental School and a local primary school in Jarabacoa at the end of February.

        I would like to know who you worked with in Jarabacoa, can we reference and visit your project, did you develop materials in Spanish or can we translate yours? We have our own K-20 project and place-based Ecological Restoration curricula and a Rain Garden sampler of activities, some of which is translated. But as I began to translate our Rain Garden Design ppt I thought houses in Madison were not the visual we needed, so I began to search and found you. I’d like to talk about possible collaboration.

      • cdoug_e says:

        yeah lets talk Rick for sure. I worked with Jamaca de Dios in jarabacoa which is a very large suburban development. By chance i stumbled into them and they were wanting to start a farm to table project a couple days later so i literally landed the job…. The wife works for FilterPure a very nice water filtration project, probably the best i have seen so far. I don’t know what the state of the project is, i lost touch with the folks over the years of being busy in Europe and the states. So i would love to collaborate, rain gardens and pit gardens like banana circles could change the tropics lots. thanks for the comment

  5. Kelly Strickler says:

    I was also really excited to read about the banana circles. It was a great idea to turn the rain gardens into a very visible and valuable resource–it is a great way to make sure they don’t get compacted or filled with trash. Rick, I’d love to hear how your project turned out. I am a graduate student in Community and Regional Planning at the University of Texas-Austin, and I am working on a preliminary feasibility study for implementing various decentralized stormwater control measures (including rain gardens) in a periurban neighborhood in Santo Domingo. The stormwater engineers from Santo Domingo I was talking with didn’t have much experience with decentralized controls, so it was difficult to get a precise estimate of material and labor costs. Did you end up building any rain gardens? How did it go? My particular project is just part of a larger, continuing community-based environmental planning project, so if you plan on continuing to work in the DR, we should get in touch anyways. Our faculty advisor who perpetuate the project has a lot of contacts that you may be able to use. (see http://soa.utexas.edu/programs/community-and-regional-planning/dual-degree-programs/crp/latin-american-studies/crp for a brief synopsis of our work). My email is Kelly.strickler@gmail.com and I would love to hear from you.

    • cdoug_e says:

      glad to see that this resource is becoming a network. Good luck in the DR. i also have a contact of an eco architect who brings students from Humboldt in Cali for a sustainability study abroad program and maybe can help you guys out as well!

    • prairierick says:

      Thanks for the post. We taught a 2-wk workshop Colaboración Ambiental at the Escuela Nacional del Medio Ambiente y Recursos Naturales in Jarabacoa on the Jimenoa and Yaque del Norte rivers. We also involved the Environmental School students with a local elementary school. The Environmental School students began a rain garden project, and are continuing it. They will also follow-up and help plant a rain garden at the elementary school. My e-mail is rdhall44!gmail.com, More info on Earth partnership at http://www.uwarboretum.org/eps.

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