What is the term for a gradual increase in land area that occurs when water recedes?

The correct term for a gradual increase in land area that occurs when water recedes is known as reliction. Reliction specifically refers to the process where land becomes exposed due to the receding of water levels, which can happen in lakes, rivers, or other bodies of water. This increase in land is recognized legally as the owner of the previously submerged land is entitled to the newly exposed land.

The other terms mentioned in the choices refer to different geological and geographical processes. Accretion, for example, describes the gradual addition of sediment or soil by natural processes, such as the buildup of sediment along riverbanks or shorelines over time, but it does not specifically involve the retreat of water. Alluvion is related to the deposits made by flowing water and can refer to increase in land, yet it does not address the receding water aspect directly. Erosion involves the wearing away and removal of soil and rock, which is quite the opposite of gaining land. Therefore, understanding that reliction focuses on the exposure of land due to water receding is essential in grasping the correct term.