A river dike, also known as a levee, is an embankment structure built along the edge of a water channel. This ridge is typically artificial and runs parallel to the river’s course. Ancient civilizations in Mesopotamia and Egypt constructed these man-made features thousands of years ago to control river flow. The term “levee” comes from the French word levée, meaning “raised.”
Primary Function of River Dikes
The primary function of a river dike is to contain the water within the channel during periods of high flow, which is its central role in flood management. By acting as a physical barrier, the embankment raises the effective height of the riverbank, preventing the water from spilling over. This containment protects adjacent low-lying land, communities, and infrastructure from inundation during seasonal flooding events.
This process isolates the river from its natural floodplain, the land area that would typically be covered by water during a flood. Containing the water reduces the risk of catastrophic damage to populated areas that have developed near the river. The dike system increases the river’s capacity to convey water safely downstream.
Dikes also play a role in channel stabilization and navigation maintenance, particularly through the use of related structures like spur dikes. These secondary structures, built perpendicular to the riverbank, redirect the flow’s energy to manage sediment distribution. By narrowing the effective channel width, dikes can increase the water velocity, which helps to deepen the channel and maintain adequate depth for commercial shipping.
Structural Design and Materials
The engineering of a modern river dike relies on creating a stable, impermeable barrier that can withstand the hydraulic pressure of floodwaters. The most common structural form is a trapezoidal cross-section, which provides a wide, stable base that tapers up to a narrower top, or crest. This design ensures the structure resists the lateral forces exerted by the water.
Dikes are primarily constructed from locally available, compacted earthen materials, such as soil, sand, and impervious clay. Clay is often incorporated into the core structure to minimize the seepage of water through the embankment, which is a major cause of failure. The exterior slopes are frequently covered with grass, rock, or riprap to prevent surface erosion from rain, waves, and overtopping water.
Foundational stability and seepage control are addressed through specific construction measures, such as cutoff trenches or internal vertical barriers. These barriers, sometimes called antiseep collars, are installed beneath the dike to extend the path water must travel to seep through the foundation. Engineers also build the dike with sufficient freeboard, which is the extra height above the anticipated high-water level, to prevent the flow from simply overtopping the structure.
Dikes Versus Other Water Barriers
While many flood control structures share the common goal of water management, river dikes are distinct from other barriers in their purpose and orientation. A river dike is a linear embankment that runs parallel to the water flow, confining the river to its channel. Its function is to protect the land on one side from the water on the other.
In contrast, a dam is a massive structure built across a river channel, completely blocking the flow to impound water and create a reservoir. Dams are designed to retain water on both sides for storage, power generation, or long-term water level control, rather than simply guiding flood flow.
Seawalls and bulkheads protect coastlines from ocean wave action and erosion. Although similar in form to a dike, their design accounts for tidal variations and the dynamic energy of ocean waves, unlike the steady pressure of river floods. Artificial river dikes should also not be confused with natural levees, which are raised banks that form naturally as a river deposits sediment during floods.