AFTERMATH: A large number of cars on Wednesday stalled on the roads after water went into their engines. Doha’s inability to deal with rainwater is exacerbated by the fact that much of the city lacks drains.

By Steff Gaulter

You may have noticed that it has been a bit wet in Qatar recently. Frankly, you can’t really have failed to notice the weather. Even if you spent your whole time inside, the chances are the water made it to you somehow, either through cracks in the windows or doors, or perhaps from a leak in the roof.
We were lucky, in that our house remained mostly water tight and there was just a small power cut to deal with. I was also rather fortunate that I had swapped my little coupe for a larger 4x4 about a year earlier. Had I attempted to get to work in my sports car on Wednesday, I’d probably still be floating around a roundabout in the centre of town. As it was, I managed to make it to the office safely, just an hour or so later than usual.
As I arrived in the office, I started seeing video clips of what else was happening in the city: the water cascading into people’s offices, huge floods were submerging cars and water was flowing freely through the new multi-billion dollar airport. I began to realise the magnitude of the flooding.
A quick glance at the rainfall statistics revealed why there was such a problem: 80.8 millimetres of rain had fallen at the airport. To put that into context, five to ten millimetres would be classed as a wet day in the UK, and 50 millimetres is reported by the World Meteorological Office as a severe weather event. Eighty millimetres is more than Doha normally receives in a year, and the majority of it fell in the space of just three hours.
Almost any location which receives its entire annual rainfall in three short hours would be flooded. Obviously there are parts of the world that would have faired better than Doha did, but the amount of disruption depends on a number of factors, including the soil type and whether the area is urban or rural.
In Qatar the sandy soil spends the majority of its life being baked hard by the sun. It cannot readily absorb moisture so any rainwater simply sits on the top of the surface, collecting into larger and larger puddles.
In Doha itself, there is an even greater chance of flooding, because urban areas are notoriously bad at absorbing water. Look around any city and you will see huge amounts of tarmac and concrete. This means that flooding is often worse in city areas than it is in the surrounding countryside, and Doha obviously has the additional disadvantage that much of the city lacks drains. The lack of drains is being addressed, as the road works around my house will testify, but it’s an immense task and Rome wasn’t built in a day.
The soil type and the large urban areas worked against the city, exacerbating the flooding making many roads impassable. However, as the water levels rose, it was interesting to see the discrepancies in the amounts of rainfall. Abu Hamour reported 31.8 mm of rain, Messaieed reported 17.8 mm, but Al Khor received just 2.4 mm. Some people have questioned whether these reports can be accurate, given the large variations in the values. I have been asked more than once if the amount of rain can really vary so greatly across such a small area.
Rainfall amounts often vary greatly from showers, which is one reason why they can therefore be a weather forecaster’s worst nightmare. The resolution of a computer models isn’t small enough to predict an individual shower, so all we can say is that showers are likely in an area. We cannot say that a shower will definitely hit a particular city at a particular time. There are simply too many processes in the atmosphere which would need to be included in a computer model, meaning the calculations would be impossible.
Shower clouds vary in size, but can be very small. One location may see torrential rain, but half a kilometre down the road, it could stay bone dry. This means that if you are forecasting the weather for an outdoor event, you would have to tell the organisers that showers are a possibility, but you couldn’t say for certain whether their event would be wet or dry.
A thunderstorm is also a shower, albeit a rather active one! We would therefore expect some parts of the city to see more rain than others. The satellite picture does show a sudden development of the storm just as it began to clear away from the coast, so it is entirely possible that the airport did receive 80 mm of rain, even though Al Khor only received 2.4 mm.
As the storm finally cleared away, the water levels quickly started to subside. One thing that always impresses me after such a huge downpour is the speed in which the water drains away. By the time I drove home from work the water had largely disappeared, with only a few muddy puddles to remind me of the exceptional amount of rain which had fallen in the morning.