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.
The in-soil storage of water depends not only on the type of land preparation but also on the type of cover or previous vegetation on the soil. Figure 15 indicates the effect of burning vegetation on the amount of water stored in the soil. Conserving fallow vegetation as a cover on the soil surface, and thus reducing evaporation, results in 4 percent more water in the soil.