A ravine is a geographical landform defined as a small, narrow, and deep valley with steep sides. It is a feature created by the persistent, erosive power of running water, often serving as a natural drainage channel for a watershed. This landform sits within a specific scale on the continuum of erosional features, being distinctly larger and more permanent than a gully but considerably smaller than a canyon.
Defining Characteristics and Scale
The physical structure of a ravine is typified by its narrow floor and steep walls. These sides can exhibit a gradient ranging from approximately 20% to 70%, creating a deep, pronounced incision in the landscape. When viewed in cross-section, a ravine often presents a distinct V-shape, a morphology that reflects the downward cutting action of the water that formed it.
While exact metrics vary globally, a ravine is generally considered to have surpassed the dimensions of a gully when its depth exceeds about five meters, or roughly sixteen feet. Water flow within the ravine channel is often intermittent, carrying significant volume only after heavy rainfall or snowmelt, though some larger ravines can sustain a small, permanent stream.
The Geological Process of Formation
The creation of a ravine is driven by the process of fluvial erosion, which is the wearing away of the land by water. This process begins when concentrated surface runoff, often due to heavy precipitation or rapid snowmelt, flows down a sloping surface. The volume and velocity of this water provide the energy needed to dislodge and transport loose soil and sediment.
The primary mechanism of growth involves two actions: vertical downcutting and headward erosion. Vertical downcutting deepens the channel by eroding the material directly beneath the flow. Headward erosion causes the ravine to lengthen, as the water flow eats away at the land at the head of the channel, pushing the origin point further upstream over time. This continuous cutting action, especially through soft or unconsolidated sediments, allows the ravine to become a permanent, deeply incised feature of the terrain.
Distinguishing Ravines from Other Landforms
The distinction between a ravine and similar landforms such as a gully, a gorge, or a canyon is determined by differences in size, permanence, and the geological material involved. A gully represents the smaller, initial stage of water-driven erosion. Gullies are often shallow and temporary features that can be easily erased or filled in by agricultural practices like plowing.
A ravine, by contrast, is a more established and permanent incision that is too large to be traversed by vehicles. Moving up in scale, a canyon or a gorge is a significantly larger and deeper landform. These features typically involve a river cutting through harder bedrock over vast geological timescales.
A gorge is often described as a deep, narrow canyon, but it is still generally larger than a ravine. While a ravine forms easily in soft soil and sediment, a gorge’s steep and rocky walls result from the river’s power to incise into resistant rock formations. The ravine occupies the middle ground, representing a substantial, permanent channel that has eroded beyond the gully stage but has not achieved the massive scale and bedrock depth of a canyon or gorge.