The process described in the question is known as aggradation. Aggradation is the process of building up the land surface by the deposition of solid material in its lower areas. This occurs when sediments, such as sand, silt, and clay, are transported and then deposited by water, wind, or ice. Over time, repeated deposition of these sediments can lead to the formation of new landforms and the gradual raising of the land surface.

Option 1: Abrasion is the process where sediments and rocks are worn down or smoothed by the friction and impact of other sediment particles. It is not directly related to the building up of land surface through deposition.

Option 2: Agglomeration refers to the process of particles or components coming together to form larger mass or cluster. It is not directly related to land surface building up through deposition.

Option 4: Attrition is the process of gradual wearing down and fragmentation of rocks and sediments by the grinding action of other sediment particles. It is not directly related to the building up of land surface through deposition.

Overall, option 3, aggradation, is the most accurate and appropriate answer as it specifically describes the process of building up the land surface by the deposition of solid material in its lower areas.