Verdaus

The city of Isfahan in built around water. Located in the centre of a vast desert plateau it owes it’s existence to the Zayandeh Rud, a river transporting water from the snow covered peaks to the west. Isfahan is famous for it’s sublime bridges built between the 12th to 18th Centuries. However, more impressive (in terms of Water Sensitive Urban Design (WSUD)) is the extensive “rain gardens” flanking the streets of the old city.

Pleasing green dappled shade dominates the character of Isfahani streets. This is a striking contrast to the dry hot and exposed streetscapes only a few hours flight away in cities on the southern side of the Gulf. The planners of Isfahan city obviously had a vision for the best urban street in this climate. Apart from comfortable scale and proportion, these streets have some of the densest urban tree planting in the world. These are a pleasing and comforting contrast to the surrounding desert expanse.

Street trees and shrubs are planted in sunken gardens adjacent to the street carriageway. These open channels are what we call today “rain gardens” or “infiltration beds” that feature in the contemporary practice of “green infrastructure” now sweeping the “developed” world. They allow stormwater to infiltrate into the ground which increase available water for street plantings and also reduce peak flows during rainfall events. Sediment drops out of stormwater by reducing flows. Rain gardens can further purify stormwater runoff through phytoremediation, using plants to filter and absorb pollutants. The rain gardens of Isfahan may not be performing this role as the right type of plant material may not the sufficient. However they are certainly helping to absorb peak flows and maintain healthy street tree plantings.

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The rain gardens are irrigated via flood irrigation (traditional agricultral method). There is a system of valves and scheduling to flood sections of the city throughout the day or week. The system appears very low tech and effective. One common objection to flood irrigation is loss of water through evaporation. However the streets are well shaded and any evaporation helps cool the street, this works very well in the hot arid climate. The impact on improving microclimate is tremendous. There are streets in Isfahan without the rain gardens and street trees, and they are bleak in comparison. Streets with rain gardens and streets trees were tangibly cooler (and much more populated) than those without.

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These 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 in 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 and aesthetic beauty is a key benefit of the green infrastructure approach. Urban vegetation plays a key role. Urban policy makers and designers alike are improving quality of life in cities by understanding and applying this principle. This shift in mindset moves away limiting urban vegetation as purely decorative or ornamental. This change is promoted by contemporary landscape architects, urban designers and scientists. Dr Kongjian Yu’s article “The Art of Survival” captures the spirit of this new but ancient call to understand and work with nature for our ease of survival.
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The sunken garden channels are bare earth and 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. This seemed necessary as all drain gardens drained to the main canals, and then the river. Standards and codes in the developed world would make this difficult to to achieve and perhaps frustrate implementation of the entire system. The open channels could be see to be be safety hazard, however there were no major tragedies during our stay. It seems the city and it’s people had accepted the “hazard” of open channels in exchange for the many benefits such as a cooler, greener city and better urban life. Small bridges allow people to cross the channels safely.
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Practitioners of Water Sensitive Urban Design (WSUD) 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.