عنوان مقاله [English]
The catastrophic flooding of Shiraz on 25 March 2019 downstream of the Qurân Gate, which resulted in the mournful death of 22 and untold financial damages, and also numerous deluges later in many Iranian provinces with upwards of 73 deaths due to drowning or collapse of residences, urges the decision-makers to consider every single stretch of land as a catchment and plan the infrastructures on it accordingly. This task requires planning from the perspective of seasoned watershed managers. Sustainable management of marginal drylands, which form some 90% of the present day Iranian Plateau, should be the most important objective of urban and rural developers if the safety and security of their occupants are expected. The utmost objective of watershed management in the 1960s was soil conservation upstream of the large dams constructed with the technical know-how of international experts. This was done to elongate the economic life of the dams and their appurtenances. It is fortunate that the new crop of watershed mangers is intent on taking an integrated approach toward solving problems. They, therefor, contemplates technical practicability, environmental soundness, financial feasibility and social acceptability in planning watershed rehabilitation by being up-to-date on the latest proven results published in scientific journals. Obviously, a paradigm shift in watershed management strategies seems necessary in the context of climate change, particularly with respect to unprecedented droughts and downpours. The question is: How to plan?
There are two schools of thought about how to mitigate flood damage. The commonly practiced engineering approach is to dam or channelize the flood. As the first alternative is very expensive and time consuming, safe water-conveyance systems are designed and constructed to get rid of the flood and decrease its damage and casualties. The watershed management approach is how to conserve soil and water by keeping as much of the runoff as possible on land encouraging vegetative cover establishment as well as the artificial recharge of groundwater if suitable areas are accessible. This alternative turns a challenge into an opportunity, particularly in a country facing a water crisis. Fortunately, this has been brought to the attention of a group of experts appointed by the Society of Legal Experts of the Province of Fars, which had been commissioned by the Islamic Body of Consultation of the City of Shiraz:
"Of the most importance and of utmost efficiency for flood-damage mitigation implemented by the Shiraz Municipality on the Qurân Watershed through bygone years is tree planting [on level terraces], especially on its eastern flank, and installation of 10 masonry check dams on one of the eastern sub-catchments that contributes runoff to the primary waterway. These have effectively controlled the runoff from that [particular] expanse."(Stamped by the seal of the Society of Legal Experts of the Province of Fars)''. Filling up a ravine that safely conducted the Qurân Gate floods to the vineyards of Sail Abad (Flood Ville in Farsi) and recharged its aquifers in order to widen the previously narrow highway resulted in a disaster unbecoming of Shiraz. It is ironic that our beloved poet Saádi (1209-1295) had warned us centuries in advance:
"Oh you, who have built a house on a floodway; the riverbed does not make a competent foundation".
And more to the point, "To rule the nature, you have to obey it". William Blake (1752-1827).
We do hope that our civil engineers have learned a hard lesson, and the colleges of engineering will include appropriate courses on watershed/aquifer management practices in their curricula.
Seyed Ahangh Kowsar