The rate at which a waterfall erodes backward is called a retreat rate. The fastest retreat rates can move a waterfall back about a meter and a half per year. Retreat can happen pretty quickly, because the rock ends up being plucked out by flowing water in large chunks.

The erosion rate of waterfalls varies dramatically based on water volume and rock hardness, ranging from several meters per year to nearly zero. Historically, a massive feature like Niagara Falls eroded at a rate of 1 to 2 meters (3 to 6 feet) per year. However, modern engineering and hydroelectric water diversion have slowed this to just 30 cm (1 foot) every 10 years. In contrast, smaller waterfalls on harder igneous rock may erode almost imperceptibly over centuries. The process typically involves "undercutting," where water wears away the softer rock layers at the base (plunge pool), causing the harder top layer (lip) to eventually collapse. Other factors, such as "transport capacity" (the ability of the river to move debris), also play a role in how quickly a waterfall retreats upstream. Without human intervention, most major waterfalls are geologically temporary features that will eventually erode themselves into a series of rapids or a steady slope over tens of thousands of years.