For those studying geography, the term relief refers to the horizontal and vertical dimensions of land surface, also known as terrain. This is particularly apparent on physical maps, which emphasize the relative height of the land with differences in color and shading for differences in height, often resembling three-dimensional surfaces, instead of emphasizing geographical boundaries of states and countries.
Relief is important in the study of geography for a number of reasons. First, a region's terrain is one of the main determinants of its suitability for successful human settlement. Rocky and steep areas are less welcoming to dwellers than flat plains that have alluvial features. Understanding an area's relief also helps planners understand how drainage works in the area. Relief maps can help planners locate watersheds, determine where water moves and predict how human activity is likely to affect water quality over time. Knowing the lay of the land also helps with planning for soil conservation, which is particularly important in the field of agriculture. Understanding cropland slopes helps determine the best angles for contour plowing and other cultivation practices. For those looking to fly into small airports, knowing the terrain often makes the difference between a smooth landing and a much less pleasant outcome.