- Retaining walls are a useful tool in preventing erosion caused by uneven topography. The addition of a retaining wall allows for land to be leveled, thereby decreasing erosion caused by wind, gravity, and rain. Retaining walls also help prevent cracks and the uneven settlement of land caused by weather and temperature fluctuations. This enables uneven areas of land to be cultivated, and provides an even surface on which to place buildings or other structures. Sand is typically used to fill low areas behind retaining walls, as it is abundant and inexpensive. This type of retaining wall is often seen near beaches and coastlines, and is sometimes used to fill, or grade, areas of uneven topography before and during building construction.
- In areas where rain is abundant, soil is vulnerable to erosion. Retaining walls prevent the sliding or washing away of soil caused by insufficient water drainage, and enable the insertion of drainage systems and pipes to carry water away from at-risk areas of land. Rainwater can be diverted into nearby riverbeds or dry wells. To be effective long-term, the retaining wall must be fortified with concrete or steel. Retaining walls can also be used for agricultural reasons to delay the seepage of water from dry areas of land, or can be used to encourage draining in areas prone to flooding.
- Retaining walls are used to separate soil from moving water sources to prevent the natural erosion caused by these marine forces. Retaining walls of this type are sometimes called seawalls, and are very effective at reducing the impact of waves and currents on surrounding landforms. Erosion caused by moving water can be significant enough to noticeably alter both soil and rock landforms over time. Retaining walls used for this purpose create a barrier between water and land, and prevent currents from pulling soil away from the shore.
