W-3


 * __Upper Course__**

Different river processes lead to different landforms.

In areas where vertical erosion is dominant – waterfalls and gorges are commonly found

In areas where lateral erosion and deposition become more important - meanders and oxbow lakes develop

In areas where deposition is the most significant process – floodplains and levees become a key aspect of the landscape.

An overview of the River Tay - a river you will study - []

Information on watersheds and drainage basins - []

Video on the Upper Course of the River Tay - []

Video on the Upper Course of the River Severn - [] media type="youtube" key="PTu8kX99hXI" height="315" width="560" Very useful animation of waterfall formation: []
 * __How is a waterfall formed?__**

Diagram of waterfall formation

1.Waterfalls are found in the upper course of a river. They usually occur where a band of hard rock lies next to soft rock. They may often start as rapids. 2. As the river passes over the hard rock, the soft rock below is eroded (worn away) more quickly than the hard rock leaving the hard rock elevated above the stream bed below. 3. The 'step' in the river bed continues to develop as the river flows over the hard rock step (Cap Rock) as a vertical drop. 4. The drop gets steeper as the river erodes the soft rock beneath by processes such as abrasion and hydraulic action. A plunge pool forms at the base of the waterfall. 5. This erosion gradually undercuts the hard rock and the plunge pool gets bigger due to further hydraulic action and abrasion. Eventually the hard cap rock is unsupported and collapses. The rocks that fall into the plunge pool will continue to enlarge it by abrasion as they are swirled around. A steep sided valley known as a gorge is left behind and as the process continues the waterfall gradually retreats upstream.

Video on how waterfalls are formed - [] Video on waterfalls, plunge pool and potholes - [] A gorge is a steep-sided valley in the upper course of the river. It is usually v-shaped. [] Video on the formation of gorges - []
 * __How are gorges formed?__**

The source of the river is where the river originates from. It is in the upper course of the long profile.
 * __What is the source?__**

A video on the source of the River Severn - []
 * __Key terms:__**


 * Waterfall**: the sudden and often vertical, drop of a river along it course


 * Gorge:** a narrow steep-sided valley