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.
Rivers erode in four ways: Abrasion or corrasion-This is when large pieces of bedload material wear away the river banks and bed. Attrition-This is when the bed load itself is eroded when sediment particles knock against the bed or each other and break, becoming more rounded and smaller. Hydraulic Action-This is when the force of water erodes softer rock. Solution or corrosion-This is when acidic water erodes rock.