Wetlands are difficult to define because of their great variation in size and location.
Marshes, bogs, swamps, vleis and sponges are examples of wetlands. Wetlands associated with streams and rivers slow floodwaters by acting as giant, shallow bowls. Water flowing into these bowls loses speed and spreads out. Plants in the wetland play an important role in holding back the water. The wetland acts as a sponge as much of the flood water is then stored in the wetland and is slowly released to downstream areas, instead of it all rushing to the sea within a few days.