The friction factor is affected by variations of fluid physical properties caused by variations in temperature and by the action of buoyancy forces. In rough channels the hydraulic resistance increases due to formation of vortices at the roughness elements leading to additional loss of flow specific energy. Three types of roughness can be distinguished: Natural roughness, which is formed as a result of long operation of pipelines.
Erosion by Glaciers. Like flowing water, flowing ice erodes the land and deposits the material elsewhere. Glaciers cause erosion in two main ways: plucking and abrasion. Both are illustrated at this link: [Insert a link to an animation showing how glaciers cause erosion by plucking and erosion.] Plucking is the process by which rocks and other sediments are picked up by a glacier.
If a river meets a barrier, either a natural dam or a fabricated one, a lake will result from the buildup of water. Underground water may rise to the surface through land shifts, erosion, or springs to make a lake. Saltwater lakes can also be created by land cutting off a part of the ocean. Essentially, wherever water gathers without an outlet, a pond or lake will form. More than 300 rivers feed Lake Baikal in Russia.