Flood Hazards in Erbil City Kurdistan Region Iraq, 2021: A Case Study

Erbil city is constructed in a flat plain with moderate gradient increasing northwards, the plain is dissected by tens of ephemeral wadis. The maximum elevation in the high lands NE of Erbil city is 1062 m (a.s.l.), whereas the elevation of the center of Erbil city is 420 m (a.s.l.). The average gradient from the highest part to the center of the city is 2.15%, increasing towards northeast to reach 4.79%. The mean annual rainfall is 365 mm, while the average monthly rainfall is about 24.42 mm. The site of the city is mainly covered by alluvial fan sediments. Towards northeast, however, the exposures of the Bia Hassan Formation, which consists of alternation of conglomerate and claystone cover considerable areas (82 km²) and form the high lands NE of Erbil city. The exposed rocks are thick claystone alternating with coarse conglomerate. Two very heavy torrential rain events have caused flash floods in Erbil city on 30th October and 17th December 2021. The rainfall intensities were 52 mm/day and 60 mm/day, respectively, causing destructive floods. The most affected areas were Zirin (north of Erbil) and Dara Too (northeast of Erbil), respectively, with very heavy property damages and tens of fatalities. The main reasons for the floods were the partially constructed embankments of the 150 m ring-road, and the urban development within large and wide drainage basins. Different climate data were used for the purpose of this article, with field checks.