Disaster was narrowly avoided this Friday, 28 November. The flooding of the Issil wadi, which crosses part of the city of Marrakech, did not occur. In fact, the wadi came very close to overflowing its banks following the torrential rain that lashed the city throughout Friday night.

The considerable rise in water levels caused hundreds, if not thousands, of Marrakchis, particularly those living near the wadi, to head out, fearing the worst. Residents of the neighbourhoods along the Issil wadi still remember that its overflowing in 2003 caused casualties and significant damage. They also remember the flood of 2 May 2011, which inundated several neighbourhoods in Marrakech, including Belbekkar, Daoudiate, Nakhil and Amerchich, and caused disruption to the city's road traffic.

However, the threat of flooding has not been dispelled, and the worst is still to be feared. In an article entitled: "The floods of the Issil wadi, upstream of Marrakech, a recurring natural risk" published by the European Scientific Journal in 2013, several Moroccan researchers concluded that the Issil wadi watershed, which dominates and overlooks the Ochre City, represents a permanent threat in terms of flooding that is not a new phenomenon. Historically, the city of Marrakech has experienced recurring floods following the overflowing of the Issil wadi. The memory of the Marrakchis holds many painful events related to this watercourse. On 27 April 1982, for example, a flood with a hydrological peak estimated at 130 m/s by the Hydraulic Basin Agency caused the destruction of around a hundred homes. Other floods of the same magnitude were observed by the residents of the Sidi Youssef Ben Ali district in 1954, 1967 and 1971, and then in 1986, 1987, 1988 and 1989. Another flood was observed in 1994 with a flow rate estimated at 70 m.

For these scientists, these floods originate at altitudes exceeding 2,000 m, a relatively rainy area that experiences intense downpours capable of generating sudden and rapid floods. The water concentration time is around 5 hours. This is a relatively short time. It would generate a rapid influx of water towards the outlet and a risk of a sudden rise in water levels and flow rates of the wadi at the entrance to the city of Marrakech.

The overflowing of the wadi is facilitated and sometimes caused, the Moroccan researchers point out, by the numerous deposits of rubble and household waste dumped into the bed of the watercourse. These deposits reduce the sections of the wadi and decrease its flow; a situation aggravated by the narrowness of certain water drainage structures, particularly bridge culverts.

And what about the authorities' response to this threat? Several development plans have been proposed, others have been executed and some are underway. They consist, among other things, of dredging and raising the banks on certain sections and building new bridges and protective walls to reinforce the banks of the wadi. These works must be reinforced by a firm ban on any dumping of waste and rubble in the wadi bed. Measures that must be further strengthened given the threat hanging over the city.