How Do River Rapids Happen?

Rapids are characteristic of many whitewater rivers where paddlers can encounter strong waves. They can pose many risks and dangers to swimmers and boaters, regardless of experience and skill. Extreme caution must be practiced when tackling turbulent rapids to avoid drowning and impact injuries.

  1. River Rapids

    • River rapids consist of fast flowing waters which can be small, short rifles or long and violent waters. River rapids can be turbulent and dangerous or they can stretch and tumble over rocky water bottoms or shallow riverbeds. Rapids form whitewater when the current appears white, violent and frothy. Whitewater rivers have significant sections of rapids and are often tackled by adventurist boaters for whitewater rafting.

    Formation

    • Rapids are caused by water flowing over and around varying resistance of rocks. As the river flows from its upper course, it meanders and bends to avoid areas of hard rock. This creates an interlocking path and alternating layers of hard and soft rock for the water to flow through. This alternating layers cause the water to tumble over because the hard rocks break up the smooth flow, causing the up and down movement of rifles.

    Landslides

    • Landslides occur when rock and earth falls down the slope due to gravity; they can cause rapids to occur in rivers. The Green River in Wyoming has rapids due to a landslide above the Yampa Canyon. Landslides can encroach on the river and cause rock layers to be undercut and rapids to form.

    Rapid Ratings

    • Rapids are divided into different classes based on the severity of the rapids and difficulty in paddling or rafting through them. Class I rapids have fast-flowing water with small waves and riffles. Class I rapids have just a few obvious obstructions. Class II rapids have waves up to 3 feet high with wide channels. Some maneuvering is required; these rapids are often tackled by novice paddlers. Class III rapids are for intermediate rafters; fast current and moderate, irregular waves are found in Class III rivers. Class IV waters have long, violent rapids and high, irregular waves. Paddlers must wind through constricted passages and drops. Class V waters have long, violent rapids, difficult routes and steep drops.