Which of the following is not a characteristic of Wadis?

The characteristic of Wadis that is not correct is "They hold permanent streams". Wadis are usually dry riverbeds or channels that contain water only during the rainy season. They are a common feature in arid and semi-arid regions, especially in the Middle East and North Africa. Wadis are usually characterized by steep craggy walls, which are formed by the erosion of the surrounding rocks and soil over a long period of time. They are often located in areas with low rainfall and are fed by intermittent streams that only flow during the rainy season. Therefore, "They hold permanent streams" is not a characteristic of Wadis.