Deadly flash flooding hits
many provinces of Iran

In recent weeks, the weather over Iran and neighbouring countries has been dominated by heavy rain, leading to widespread flooding with significant social and economic impacts. The intensity of this rainfall, coupled with the nature of the terrain, has caused deadly flash flooding.

Figure 1: JBA's 1-in-50-year Iran 30m river flood map for the city of Khorramabad, located in the Lorestan region in south-west Iran, one of the worst affected areas (JBA Risk Management).

The unfolding floods

Since the beginning of 2019, countries across the Middle East have experienced heavy rainfall that has resulted in flooding in Saudi Arabia, Iraq, Israel, Jordan, Pakistan and Afghanistan. In recent weeks, the accumulation and intensity of rainfall has led to widespread flooding across Iran, especially in the south-west and north-east of the country.

Flooding began in late January when the south-western Iranian regions of Khuzestan, Lorestan and Ilam experienced heavy rainfall. The rain returned in early March to eastern Iran and, later in the month, the northern provinces of Golestan and Mazandaran were badly affected.

Daily rainfall totals of well over 100mm were recorded, with some places suffering two or three rainfall events of similar magnitude (Table 1).

Table 1: Selected daily rainfall totals recorded over Iran during early 2019 (data source: Floodlist, 2019)

During the last two weeks of March, a large part of the south, west and north-east of Iran received between 200 and 500mm of rain (Figure 2).

Figure 2: Accumulated rainfall for Iran for the period 18 to 31 March 2019 (data source: NASA PMM, 2019)

To place these values in context, the average annual rainfall for Khorramabad, one of the worst affected cities, is around 500 mm. The city received almost half its average rainfall in just one week. Many regions of Iran away from the mountain ranges and Caspian Sea coastal fringe only receive between 140 and 240mm per year (Vaghefi et al, 2019).

Flood impacts

In total, the floods have resulted in an estimated 70 fatalities at the time of writing (The Guardian, 2019). In the deadliest event, 21 people died in flash flooding in the city of Shiraz; the flooding also caused hundreds of cars to be swept through flooded suburbs. Roads, bridges and other infrastructure have been damaged or destroyed by the floods. The airport at Khorramabad was submerged for a time and it has been estimated that 54,000 homes have been destroyed and another 90,000 damaged (ReliefWeb, 2019). Damage to agriculture is already estimated at around USD $350 million as flooding covers large swaths of land (Figure 3) (Reuters, 2019).

So, is this flooding unusual for a country that is classified almost entirely as either arid or semi-arid?

Figure 3: Satellite image showing the comparison of land area flooded along the Iran-Irag border on 3 April 2018 (left) and 28 March 2019 (right). Dark areas in the centre of each image indicate flooded areas (image source: NASA Earth Observatory)

Iran's history of flooding

In an average year, three quarters of Iran’s rain falls between December and March. Two factors act to concentrate this rainfall in a way that can lead to disastrous flooding. Firstly, the Zagros mountain range running across south-west Iran and the Alborz mountains in the north-east both act as barriers to the flow of air, keeping the centre of the country dry as the rain is deposited on the windward side of the high ground. Secondly, a combination of land use, soil type and terrain characterised by steep-sided valleys means that a large amount of rainfall fails to penetrate the ground and runs off rapidly, leading to flash flooding (Vaghefi et al, 2019).

These geophysical conditions mean that flooding is Iran’s second most common natural hazard after earthquakes (Figure 4). The current event is the worst for many years but Iran has suffered comparable flooding regularly throughout recent history. In August 2001, 247 people were killed in Golestan province in what was described as a “once in 200-year” flood and in 1986, flooding resulted in at least 200 deaths (Vaghefi et al, 2019; Dartmouth Flood Observatory, 2019).

Figure 4: Main hazard risks to Iran, measured by number of people affected, for the period 1985-2018 (source: World Bank, 2019)

Future flood potential and implications for insurance

After a dry spell, rain is forecast to return at the end of this week, w/c 8 April. With rivers still high, the risk of further flooding remains. In the long term, research on the implications of climate change for rainfall over Iran are inconclusive, partly because the atmospheric drivers that influence global weather patterns are relatively weak in this part of the world (Tabari and Willems, 2016).

As the government considers assigning USD $2.25 billion of state funds to help recovery efforts, it’s worth noting that non-life insurance penetration in Iran is estimated by the state reinsurer, Iranian Re, to represent around 1.84% of the GDP in 2016 (Iranian Re). This is low when compared to countries such as the UK (12.8%) or US (11.2%) and once again raises the question as to whether a state-led disaster fund in Iran should be set up to reimburse households affected by natural disaster events (OECD, 2019; Aljazeera, 2019).

JBA Risk Management has nationwide return period flood maps available for Iran at 30m resolution. For more information, get in touch.

References

Aljazeera. 2019. Iran: Deadly floods highlight need for 'natural disasters' fund. [online] Available at: https://www.aljazeera.com/news/2019/04/iran-deadly-floods-highlight-natural-disasters-fund-190410111734247.html [Accessed 11 Apr. 2019].

Dartmouth Flood Observatory. 2019. Global Active Archive of Large Flood Events. [online] Available at: http://www.dartmouth.edu/~floods/Archives/1986sum.htm [Accessed 9 Apr. 2019].
Floodlist. 2019. [online] Available at: http://floodlist.com/asia [Accessed 9 Apr. 2019].

The Guardian. 2019. Six more towns evacuated in Iran with more floods expected. [online] Available at:
https://www.theguardian.com/world/2019/apr/06/iran-six-towns-evacuated-more-floods-expected [Accessed 9 Apr. 2019].

Iranian Re. An Overview of Iran Insurance Industry. [online] Available at: http://www.iranianre.com/an-overview-of-iran-insurance-industry/ [Accessed 11 Apr. 2019]

NASA Precipitation Measurement Missions. 2019. Global Precipitation Measurements. [online] Available at: https://pmm.nasa.gov/data-access/downloads/gpm [Accessed 10 Apr. 2019].

Organisation for Economic Co-operation and Development (OECD). 2019. [online] Available at:
https://stats.oecd.org [Accessed 11 Apr. 2019].

ReliefWeb. 2019. Islamic State of Iran Situation Overview: Floods. [online] Available at: https://reliefweb.int/sites/reliefweb.int/files/resources/Iran%20-%20Situation%20Overview%20-%20Floods%20-%209%20April%202019.pdf%20v2.3.pdf [Accessed 10 Apr. 2019].

Reuters. 2019. Iran reports massive flood damage to farms. [online] Available at: https://www.reuters.com/article/us-iran-floods/iran-reports-massive-flood-damage-to-farms-idUSKCN1RG1QG [Accessed 9 Apr. 2019].

Tabari, H. and Willems, P. 2016. Daily Precipitation Extremes in Iran: Decadal Anomalies and Possible Drivers. Journal of the American Water Resources Association. 52(2) pp.541-559.

Vaghefi, S.A., Keykhai, M., Jahanbakhshi, F., Sheikholeslami, J., Ahmadi, A., Yang, H. and Abbaspour, K.C. 2019. The Future of Extreme Climate in Iran. Scientific Reports 9, Article 1464.

World Bank. 2019. Climate Knowledge Portal. [online] Available at: https://climateknowledgeportal.worldbank.org/country/iran [Accessed 9 Apr. 2019].

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