The answer is a plain.
I believe it is PLAIN
Floodplain
Floodplain
Floodplain
Kansas
A broad, flat area of land that is higher than the land surrounding it is referred to as a plateau. It may also be referred to as tableland, mesa, butte, terrace, table hill, tuya, table mountain, or flat.
Floodplain
A broad valley is a large low-lying area of land between hills or mountains. It typically has a wide expanse of flat land and is often formed by the erosion of a river or glacier over time. Broad valleys are important for agriculture, settlements, and transportation routes.
Great Plains.
A flat surface; especially, a broad, level, elevated area of land; a table-land., An ornamental dish for the table; a tray or salver.
a broad area of flat or gently rolling land is called a plain.
A coastal plain is a broad level area of land that is close to sea level. Coastal plains are formed by the accumulation of sediments from rivers and coastal processes, resulting in a flat and low-lying landscape that stretches along the coastline.