knickpoints

A knickpoint is a location along a river’s longitudinal profile where there is a sharp change in gradient, often appearing as a waterfall, rapid, or abrupt step in the basin’s bedrock. Knickpoints mark positions where incision rates differ markedly along the river and can create or be associated with fluvial terraces as the landscape adjusts to changing conditions.

Knickpoints form and migrate due to a combination of factors. Changes in base level, such as sea level fall or uplift of the land, can cause rivers to incise more rapidly and create knickpoints. Differences in rock strength, such as a harder rock overlying softer rock, can produce abrupt declines in erosion resistance, forming steps in the profile. Climate variations that increase discharge or energy available for erosion can also initiate or enhance knickpoints. Over time, knickpoints tend to migrate upstream as erosion proceeds at the distal end of the profile, leaving behind terraces and other geomorphic records of past incision.

Along with their formation, knickpoints are useful indicators in geomorphology. They reflect disequilibrium in river profiles, record uplift histories, and help estimate incision rates and tectonic or climatic changes over geological timescales. Detection typically relies on analyzing a river’s longitudinal profile, often using digital elevation data to identify breaks in slope, convexities, or abrupt steps.

Knickpoints vary in size and persistence: some are transient features while others can migrate slowly for long distances, sometimes developing into persistent bedrock steps or disappearing as conditions change and new base levels or lithologies dominate.