Rain Gardens of Isfahan

The city of Isfahan is built around water in the centre of a vast desert plateau. The Zayandeh River, supplies water to the city from snow melt originating in the Zagros  mountain range 200 kms  to the west. Isfahan is famous for it’s bridges spanning the Zayandeh, most were built between the 12th and 18th Centuries. However the less publicised “rain gardens” of the old city are an equally impressive engineering achievement.

A pleasant dappled shade dominates the character of Isfahani streets. This is a striking and welcome contrast to the exposed expanse of surrounding desert. Environmental comfort on the Isfahani street far surpasses the hot and exposed  streetscapes only a few hours flight away, in the cities on the southern side of the Gulf. The planners of Isfahan obviously had a clear vision of what makes a city street work in this harsh environment. These streets have some of the densest urban tree planting in the world.

The city of Isfahan has some of the densest street tree planting in the world.

 

Street trees and shrubs are planted in sunken gardens adjacent to the main carriageway. Today these open channels are called “rain gardens” or “infiltration beds”. These are part of the contemporary movement known as “green infrastructure” now sweeping the “developed” world. The rain gardens allow stormwater to infiltrate into the ground which can increase groundwater recharge and reduce peak flood flows.

Rain gardens address quality as well as quantity of stormwater runoff. The vegetation slows the rate of flow and so reduces sediment in the runoff. Rain gardens can further purify the stormwater runoff through phytoremediation, a process using plants and micro-organisms to filter and absorb pollutants.

The rain gardens of Isfahan are irrigated via flood irrigation (a traditional agricultural method). A system of manually operated valves are programmed to flood rain gardens on a regular schedule. The system is low tech and effective.

Manual value open to flood the rain gardens.

 

One common objection to flood irrigation is loss of water through evaporation. In this case the streets are well shaded.  Evaporation that does occur helps to cool the street, and is working very well in the dry heat of the desert plateau. The impact on improving microclimate is tremendous. Streets without the rain gardens are punishingly hot in comparison. Streets with rain gardens are tangibly cooler (and more populated) than those without.

The shaded streets of Isfahan are cool and crowded even in the summer months.

 

The rain gardens probably date from the time of laying out the streets in the 16 Century. This was the time of Sheikh Bahai (1547 – 1621), a scholar, philosopher, architect, mathematician, astronomer and poet of 16th-century Iran. “There is also no doubt about his mastery of topography. The best instance of this is the directing of the water of the Zayandeh River to different areas of Isfahan. He designed a canal called Zarrin Kamar in Isfahan which is one of Iran’s greatest canals.” Source: Sheikh Bahai Prominent Scholar of Safavid Era.

Coupling environmental function with aesthetic beauty is tied to the green infrastructure approach. Urban vegetation plays a key role. Today, urban policy makers and designers are improving quality of life in cities by understanding and applying this principle. This approach moves away from using urban vegetation as a mainly decorative or ornamental feature. Contemporary landscape architects, such as Dr Kongjian Yu support this move, as well as emerging engineers and environmental scientists. Dr Kongjian Yu’s article  “The Art of Survival” captures the spirit of this new but ancient call to work with nature so to increase the ease of survival. Call it sustainability.

The rain gardens in Isfahan are bare earth yet free from rubbish or standing water. The city maintains them well. In some areas the bottom of the rain garden can be over 600mm below the adjacent footpath or road. All rain gardens drain to the main canals, and finally to the river.

The rain gardens drain to larger channels and finally to the river.

 

Standards and codes in the developed world would not allow this difference in level and perhaps frustrate implementation of the entire system. The open channels could be seen as a safety hazard. Throughout the city small bridges allowed people to cross the channels safely. The people and stewards of Isfahan had accepted the potential “hazard” of open channels in exchange for a cooler, greener city, and a better quality urban life. Did the ancient Persians get it right?

Small bridges allow people to cross over the rain gardens.

 

Practitioners of Water Sensitive Urban Design (WSUD) today would be interested to visit the city of Isfahan. It is a shining example of using simple techniques to improve the quality of urban life through working with natural systems and urban vegetation.

The streets of Isfahan are designed to be heavily shaded during the summer. Did the Persians get it right?

27 Comments

  1. Have bookmarked this particular post, many thanks considerably!

  2. Great stuff and it is such a logical process. It makes me think about a old saying: We don’t invent new ideas we just reinvent old ones!
    Treating water runoff at source benefits the environment; it is us who need to blend in with nature as these communities have proven over time
    Thanks for the insight and proves what we need to do in our own communties

  3. Tim Conybeare

    Great article Laith, it’s wonderful to see ancient agricultural practices serving an important urban function and with such success. Also good to see, as you say, that it has struck a chord with your readers. Here in South Australia there are 2 major concerns around water; 1) efficiency and 2) flood mitigation. There has been a big environmental push away from flood irrigation techniques in agricultural areas due to the vast amounts of surface water spread over a very thin profile which of course leads to high rates of water loss through evaporation. The advantage in the situation you show here in Isfahan is that the basins are narrow and seemingly deep and appear very heavily shaded. I wonder how efficient it would be in the early days of establishment where you have less natural shade? Couple this with Mikes comments about safety and perhaps a grate or covered culvert sytem provides the answer.. check this out as a first step http://teamgalileo.wikispaces.com/file/view/Little+Bourke+Street+Rain+Gardens.pdf …It seems the flood mitigation aspect could easily be covered with some clever engineering around overland flow paths and setting some strategic invert levels to catch major storm flows and distribute them more evenly and efficiently in heavy rain events. Is flooding an issue in Isfahan? There are such great possibilities with this scheme – havesting, under pavement storage and reuse. Food for thought!

    • Laith Wark

      Tim – Thanks for your comments, from the land of WSUD. Thanks also for the link to information on the Little Bourke Street Rain Gardens. This shows how cleanly green infrastructure can be integrated in the streetscape. Neat work. This also closes the loop in my mind regarding implementation. The Isfahani Rain Gardens function so well, add such a high degree of amenity and beauty, however the detailing could be improved quite a bit. The Little Bourke Street examples demonstrate the difference detailing can make to the final presentation. I would like to show these examples to the Persians. Nice one. Thank you.

  4. Michael Cunningham

    I took the train across the Balochistan desert from Quetta to Zahedan – in SW Iran, close to where the Afghan, Iran and Pakistan borders meet – in June 1972, and discovered en route why hot sandy desert dwellers are swathed in layer upon layer of clothing – the constant wind and sand sucks out moisture, the layers prevent dehydration and provide insulation against the heat. While Isfahan’s climate will be more temperate, I can see the virtue of the shade and moisturisation in modifying the local climate. As suggested, excessive emphasis on risk/health and safety/legal remedies make it harder to apply such solutions in Westernised countries, but there may be solutions feasible in a wealthier economy, such as (removable) grids flush with pavement and road surfaces which allow safe access yet allow passage of rain and floodwater. They are used in Brisbane on a very small scale (tree surrounds), incorporation of an Isfahan-style channel might be feasible in new, and some old, developments. Trenches will be dug for National Broadband network – perhaps they could double as planted channels, rather than closed over. At present we use raised kerbs to contain stormwater on roads and channel it to drains, a flush-covered, kerbless, channel would improve access.

    • Laith Wark

      Mike – I believe Australia is one of the most regulated countries in the world. Your right, if these type of devices were installed in Australia they would need to be modified. This post generated a lot of interest, it seemed to have struck a chord with many people. Why are not our streets this good? Thanks for your comment.

  5. Jamal Alzeedi

    Laith,
    Very interesting and inspiring.
    If applied in Oman, it might assist in solving the everlasting flooding problems in Muscat despite rarity of rain fall.
    As well as making Muscat a more pedestrian friendly city, which it isn’t at the moment.
    Cheers

    • Laith Wark

      Ya Jamal – your comments are spot on. Even though rainfall in Muscat is rare, flooding is a major problem as you know. All of the impervious surfaces collect, convey and concentrate stormwater runoff. What if we made the city more like a sponge? Rain gardens in all streets. Encourage water to infiltrate locally as much as possible. And make a greener city at the same time, more friendly for pedestrians, cooler, more biodiversity…I am repeating what you say! Also we use the Ghaff tree as much as possible – imagine the character of Muscat, tunnels of green, even better than it is today!

  6. Brigette Dahm

    Hi Laith – great to see your name again! And a very inspiring set of images. It would be wonderful to see the streets of Brisbane look like that.

    Someone put your article on my desk, knowing that I’ve been compiling info re water detention and infiltration in road reserves. What I’ve been struggling to find is hard data on the impacts of increased moisture and tree roots where these penetrate beneath road pavements. That doesn’t seem to be a major issue for Isfahan, although perhaps the ground under the carriageway is too compacted to let them in. I might run some of your photos past engineers and see what kind of reaction I get.

    Hope you and Melanie are both well.

    • Laith Wark

      Hi Brigette – great to hear from you! and glad you found the post interesting. I would be very interested to know what the engineers think about the photos. I did not see any effects on the road surface that water in the sub-base might have caused. This surprised me as it is one issue that is raised as a concern. Hope to hear what the engs say…you can email me at laith@verdaus.com if you don’t mind to. Thanks for commenting and adding an interesting angle.

  7. Laith – inspiring to see what can be accomplished in a society which has its value system sorted.

    I am also certain there are design solutions and fairly minor modifications to the approach which would make it “safe” and viable in western cities.

    I love the idea of having a system which infiltrates when it is wet but which is allowed to be dependent on mains water when it is dry however there may be a better way of doing it. If they were to start cleaning their sewage (secondary + disinfection – leaving it clear + safe but full of fertiliser) and then irrigating gardens with treated effluent during the dry period. At least that way only wet period runoff will reach the river and will dilute the effluent when it is not needed leaving the river much cleaner and with more water.

    • Laith Wark

      Hi Mark. I’m glad you found the post worthwhile reading. Thank you for your input, I like your suggestion of using treated wastewater for irrigation these rain gardens during the dry season. I agree it could work very well to: 1) enhance plant growth and health, and 2) reduce pollution in the local river. I think that could work technically, now how to make the right connection to get something started!?

  8. Michael Erickson

    Hi Laith,

    This is a very good article and makes me think a lot. I have seen similar ‘catchment’ older devices in streets in both Noosa Australia and at Oxford England but neither supply water (or at least not maybe intended) for plant growth- I am guessing they need a certian raining ‘regime’ to work – maybe its a modest level of rainfall with some frequent heavy events – Could maybe work well in mid and southern Asia new cities..

    I like the theme that none of this is new but good common sense with a sprinkling of creativity.

    Thanks

    • Laith Wark

      Hi Michael
      Thanks for the comments. You raised a good point regarding water supply to sustain the plants. Irrigation water in Isfahan comes from piped supply. I do not know the source, it could be the same as the city potable water supply. I would like to find out. The river itself is polluted from wastewater discharge…the local Sewerage Treatment Plants are over capacity. Perhaps wastewater could be treated via phytoremediation (reed beds / constructed wetlands)…an additional function for new streets? (a lot of development happening there now). It would be important to integrate design of such reed beds with stormwater function, a worthwhile topic of study.
      As you say parts of Asia where rainfall is more regular may not need additional irrigation. In these cases the stormwater function would become more important. Street trees and plants would be sustained by the natural rainfall – more true to the principle of the rain garden.
      Thanks for commenting, it’s good to hear from you, and food for thought.

  9. Hi Laith, Extremely useful article. Has quite a few important lessons to those struggling with the question of soft infrastructural options, especially in the context of developing societies. Hope we can keep the topic alive by bringing together other illustrative examples. Thanks for the excellent documentation.

    • Laith Wark

      Hi Mohan, Glad you found the article useful. I immediately thought of India when I saw these rain gardens working in Iran. Very different countries with different issues for sure, but local knowhow, polical will and thoughtful design could uncover an appropriate solution in India I am sure. Thanks for your commment, and well done on what you are doing with Integrated Design.

  10. Laith Wark

    Andrew, glad you found it interesting. One detail of these rain gardens that is particularly interesting is the kerb (or no-kerb) detail. In most cases there is no kerb at the edge of the carriageway. In places there is as much as 600mm drop into the rain garden. Because it is an obvious hazard people take extra care not to get too close to the edge – they slow down. The effect is better behaved traffic in the city centre…the engineer who I believed designed it, Sheikh Bahai Prominent Scholar of Safavid Era, was also a poet. Based on the postive outcome we could do with a few more engineer-poets today :)

  11. Adarsha

    This is quite inspiring… The same technique was also in use in a lot of ancient civilization. It was not used directly, but the principles were slightly different to suit the conditions at that time.

    • Laith Wark

      Adarsha. Glad you found this inspiring. I think you are right and that there must be many “old” examples “new” practices throughtout the world. This is one of many water related aspects in Isfahan that are very interesting. The city itself is an excellent example of sustainable development in many respects.

  12. Brian D'Arcy

    Thanks Laith, inspirational and good messages for people wondering what green infrastructure will be like in a decade or so…

  13. Laith,
    Does the municipal authority have a special team to maintain the rain gardens? Or is it their parks people…

    • Laith Wark

      Andrew. Good question – maintenance is the key. I observed municipality staff removing trash from the rain gardens. However maintaning and monitoring the irrigation part may be a speacial department. I would need to research this to find out what would be the maintaince resposibilities. Also it is not clear what the maintenance regime is. However it appears to have worked for the last 400 years or so. I would be interested to know what level of pollutants would be in the soil after all this time and whether it is a problem. Your question raises a very good point and I am interested to find out more, perhaps on my next visit to Isfahan, or via a contact there. Will let you know if I find out. (PS. Saw your post on China and treatment at point of use, very interesting and insightful.)

  14. Lachlan Bain

    Great stuff Laith. Simple and effective. Next logical step would be to combine the idea of flood irrigation in the dry season with some level of urban farming. Rice paddies / vegetables along the roadside.

    • Laith Wark

      Lachlan. Glad you found this post interesting. Question regarding the urban farming…the runoff flows straight off the road carriageway into the gardens…what would be the impact on any food crops?

  15. miguelito pegi

    yes I agree with Ian, there is a similarity of technique used in my country.

  16. its very interesting laith, because that principle currently used on rice farming here in Mindanao and some part of the Philippines agricultural area. but I did not expect that can be possible on urban area

    it’s a very impressive energy and water conservation way of Isfahan,iran

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