Flooding kills at least thirteen people in southern Iran.

At least thirteen people have died in flooding across southern Iran between Friday 20 and Monday 23 March 2020. The worst of the flooding has been reported in Fars and Hormozgan provinces, each of which have suffered at least five casualties, Bushehr where two deaths have been confirmed, and Qom, which has also recorded a single death, but floods have also occurred in Kerman, Sistan,  Baluchestan, Gilan, Kohgiluyeh & Boyer-Ahmad, and Golestan provinces. Flooding has also been recorded in neighbouring areas of Iraq and Saudi Arabia.

Flooding in southern Iran in March 2020. Jonoub Fouri/Twitter.

The Middle East, while generally arid, is prone to occasional severe flooding. This stems from two causes; firstly the arid climate prevents the development of a thick soil layer which would be expected in less dry areas, so that in much of the area (non-porous) bedrock is either exposed or close to the surface, and secondly the hot climate leads to heavy evaporation from nearby seas and oceans, so that if the wind changes direction and brings water-laden air to the area, it brings a lot of precipitation with it. This combination of heavy rainfall and low ground absorbency leads to large amounts of water at the surface, typically moving downhill at some speed. Wadis, dry channels or ravines through which these sudden floods are channelled, can be particularly dangerous at these times, particularly as they often appear to resemble natural pathways or even camp sites to people unfamiliar with the climate.

Flooding in southern Iran in March 2020. Tasnim News Agency.

The storms have been caused by a low pressure system over the eastern Mediterranean, caused by hot weather in the region, a common problem during spring in the region. As the air is heated the the air pressure drops and the air rises, causing new air to rush in from outside the forming storm zone. If this zone is sufficiently large, then it will be influenced by the Coriolis Effect, which loosely speaking means the winds closer to the equator will be faster than those further away, causing the storm to rotate, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

 Debris left by flooding in southern Iran in March 2020. Dobrinich Channel/YouTube.

Whilst the high winds associated these storms is extremely dangerous, the real danger from such storms is often the flooding. Each millibar drop in air pressure can lead to a 1 cm rise in sea level, and large storms can be accompanied by storm surges several meters high. This tends to be accompanied by high levels of rainfall, caused by water picked up by the storm while still at sea, which can lead to flooding, swollen rivers and landslides; which occur when waterlogged soils on hill slopes lose their cohesion and slump downwards, over whatever happens to be in their path.

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Evarcha dena: A new species of Jumping Spider from the Zagros Mountains of southwest Iran.

Jumping Spiders, Salticidae, are the largest family of Spiders, with about 5800 described species in 600 genera, roughly 13% of all described species. They are noted for their exceptional vision, possibly the best of any Arthropods, which is used in hunting, with these Spiders being active hunters that stalk their prey before catching it with a final leap, as well as in mating, with many species having evolved elaborate courtship rituals. The genus Evarcha currently contains 89 species from across the globe, though it may be paraphyletic (i.e. the members of the genus may not all be descended from a single common ancestor). These Spiders tend to be dull in colour, and favour low plants in moist areas.

In a paper published in the journal Peckhamia on 30 April 2017, Alireza Zamani of the Department of Animal Biology at the University of Tehran, Amin Hosseinpour of the Department of Medical Entomology and Vector Control at Shiraz University of Medical Sciences, and Koroush Azizi and Aboozar Soltani of the Research Center for Health Sciences at the Institute of Health and Department of Medical Entomology and Vector Control at Shiraz University of Medical Sciences, describe a new species of Evarcha from the Zagros Mountains of southwest Iran.

The new species is named Evarcha dena, in reference to Mount Dena, a prominent landmark in the area where the species was discovered. The species is described from two male specimens, one found close to the village of Rahmali in Kabgian District, and the other in the Park-e Jangali forest park, both in the province of Kohgiluyeh & Boyer-Ahmad. These are slightly over 8 mm in length, with oval abdomens, and are black in colour with a row of grey hair along their medial line.

Evarcha dena, male. (A) Dorsal view. (B) Ventral view. (C) Prosoma, frontal view. Zamani et al. (2017).

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