Floods in Saudi Arabia kill 16 people

Sixteen people have been killed and three more are still missing after flash flooding hit parts of Saudi Arabia.

The downpours have struck across the length and breadth of the country, from Hail in the north to Baha in the south. The capital Riyadh has also been swamped by heavy rain.

Thunderstorms have lashed many parts of the Arabian Peninsula over the last week. Two people in Oman are also known to have lost their lives in the weather.

Although the Arabian Peninsula generally has a very low annual rainfall of approximately 75mm of rain per year, flooding is not uncommon.

The majority of cities do not have a drainage system, which means that heavy thunderstorms often cause flooding in built-up areas.

In the surrounding desert landscape, the ground is baked hard by the sun for the majority of the year, meaning it cannot quickly absorb moisture.

If the ground is flat, the rainwater will simply sit on the surface until it evaporates. However, if the terrain is mountainous, the rainwater will hurtle down the mountainside, pouring into valleys.

The valleys, known as wadis across the region, remain dry for most of the year, and only fill during the rains.

Wadis can be dangerous. It may be sunny on the coast, but pouring in the mountains and the wadis can become a raging torrent in a matter of minutes, with little or no warning for those on the coast.

The weather across the Arabian Peninsula is promising to stay very unsettled over the next few days, so more flash flooding looks likely.