Fine-grained soil, or clay, mixed with water.

Muddy water

Mud left behind in a street after a flood.

Mud is really simply clay. It is the material that quickly colours the water during times of high flow and flood. Mud is left behind after a flood, coating the floors and walls of flooded buildings.

Clay and mud are also the most fertile part of the material carried by a river, so that when mud is laid down over a floodplain during a flood, it brings natural fertility to the land.

In the past, people relied on the clay brought by a flood. The Nile flood is the most famous. Every year it flooded the lower Nile River in Egypt and brought both water and fertilizer. When the flood went down, the farmers then grew their crops. This flood enabled farmers to grow enough for the Egyptians to eat for thousands of years. However, following the building of the Aswan High Dam, the flood no longer occurs and so the lower Nile no longer receives its annual supply of clay.