Answer:
Floodplain.
Step-by-step explanation:
Floodplain is a fully developed flat land that stretched from either side of a river, which experience flood during heavy rain or snowmelt. Floodplain soil is rich in nutrients due to mud brought by the river to these flat land and this place is ideal for growing food crops due to nutritive soil that produces high yield and that's why people settles in these flat land near the rivers.