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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Magnitude 5.5 Earthquake in Bushehr Province, Iran.

The United States Geological Survey recorded a Magnitude 5.5 Earthquake at a depth of 10.0 km in Bushehr Province, Iran, slightly before 11.05 am local time (slightly before 6.35 am GMT) on Thursday 19 April 2018. There are no reports of any damage or casualties associated with this event, but it was felt in coastal areas around the Persian Gulf, including Iran, Kuwait, Saudi Arabia, Qatar and the United Arab Emirates.

The approximate location of the 18 April 2018 Bushehr Earthquake. USGS.

Iran is situated on the southern margin of the Eurasian Plate. Immediately to the south lies the Arabian Plate, which is being pushed northward by the impact of Africa from the south. This has created a zone of faulting and fold mountains along the southwest coast of the country, known as the Zagros Thrust Belt, while to the northeast of this the geology is dominated by three large tectonic blocks, the Central Iran, Lut and Helmand, which move separately in response to pressure from the south, stretching and compressing the rock layers close to the surface and creating frequent Earthquakes, some of which can be very large.

The movement of the Arabian Plate and extent of the Zagros Thrust Belt. Rasoul Sorkhabi/Geo ExPro.

To the northeast of this the geology is dominated by three large tectonic blocks, the Central Iran, Lut and Helmand, which move separately in response to pressure from the south, stretching and compressing the rock layers close to the surface and again creating frequent Earthquakes.

The population of Iran is particularly at risk from Earthquakes as, unlike most other Earthquake-prone nations, very few buildings in the country are quake-resistant. The majority of residential buildings in Iran are made of mud-brick, a building material particularly vulnerable to Earthquakes as the bricks often liquefy, trapping people inside and quickly asphyxiating them with dust. This is particularly dangerous at night when the majority of people are inside sleeping.

 Section through the Zagros Fold Belt. Sarkarinejad & Azizi (2007).

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

 

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Two Earthquakes in southern Iran.

The United States Geological Survey recorded a Magnitude 4.9 Earthquake at a depth of 44 km roughly 25 km to the southeast of the city of Khvomuj in southern Bushehr Province, Iran, slightly after 12.35 pm local time (slightly after 9.05 am GMT) on Tuesday 19 November 2013. This was followed by a second quake with a Magnitude of 4.6 at a depth of 27.4 km, 10 km to the northwest of the city of Arad in Fars Province, slightly after 5.00 pm local time (slightly after 1.30 pm GMT) on the same day. These are moderately large quakes, and are likely to have been felt across a wide area, though there are no reports of any damage or casualties.

The locations of the two 19 November 2013 southern Iran Earthquakes. The Bushehr Province quake is purple and the Fars Province quake is red. Google Maps.

Iran is situated on the southern margin of the Eurasian Plate. Immediately to the south lies the Arabian Plate, which is being pushed northward by the impact of Africa from the south. This has created a zone of faulting and fold mountains along the southwest coast of the country, known as the Zagros Thrust Belt, while to the northeast of this the geology is dominated by three large tectonic blocks, the Central Iran, Lut and Helmand, which move separately in response to pressure from the south, stretching and compressing the rock layers close to the surface and creating frequent Earthquakes, some of which can be very large.

The population of Iran is particularly at risk from Earthquakes as, unlike other Earthquake-prone nations, very few buildings in the country are quake-resistant. The majority of residential buildings in Iran are made of mud-brick, a building material particularly vulnerable to Earthquakes as the bricks often liquify, trapping people inside and quickly asphyxiating them with dust. This is particularly dangerous at night when the majority of people are inside sleeping, but it is to be hoped that this quake, which occurred in the late afternoon has caused less casualties than some historic nighttime quakes.

See also Magnitude 4.8 Earthquake in Markazi Province, eastern Iran, Magnitude 4.2 Earthquake in Khuzestan Province, southwest Iran, Magnitude 4.4 Earthquake in northwest Iran, Magnitude 4.2 Earthquake in Semnan Province, northern Iran and Magnitude 4.5 Earthquake in the Zagros Mountains of western Iran.

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