Freeing the Elwha (River Flows and Sediment Movement)
OverviewSeasonal weather patterns affect the flow patterns of water into the rivers (and watersheds) of western North America. What landform features can form when erosion is caused by fast –moving water from Spring and Fall rains, and snowpack melt off?
The focus of this lesson is to learn about the seasonal flow patterns of rivers in western North America, and the erosional effects of fast-moving water. Rivers in the west tend to experience high flows during the spring rains and snowpack melt off, low flows during the long summer drought, increased flows during the return of the fall rains, and slightly lower flows in winter when much of the precipitation is trapped as snow. However, strong storms can result in sudden spikes of water flows and flash flooding.
Fast-flowing rivers can move large stones and carry a lot of sediment, so they have the ability to pluck stones from the bedrock and can carve deep canyons. Eventually fast-flowing rivers form V-shaped valleys, with terraces/benches forming along former riverbeds. Where flows reach steep gradients, rapids and waterfalls will form. The goal of this lesson is to demonstrate the features that can form in these fast-flowing streams
V-shaped valley: A steep valley carved by a fast-flowing river that takes on a shape that resembles a V.
Terrace/bench: A generally flat area elevated above a river, which at one time was the former riverbed, before the river eroded deeper into the basin.
Rapids:A sudden change in gradient, particularly over erosion-resistant materials, will cause the river to become turbulent and the velocity increases.
Waterfall: A cascade of falling water where there is a vertical or almost vertical step in a river.
Kolk: A vortex in a fast-flowing river, which plucks river bed material, forming a depression in the rock and often a pool or pond.
Lesson 3- River Flows and Sediment Movement.pptx
- Waterfalls and Headward Erosion.pptx
- Stream Table
Reflection Journal Pages (printable handout)
Vocabulary Notes Page (printable handout)
Review the Essential Question, introduce the Guiding Question.
Students should take a few minutes to respond to the reflection prompts. Discuss their answers and any questions they've generated.
Hand out Vocabulary Notes. Review the words. Students can define words as they watch the PowerPoint Lesson.
Present the PowerPoint Lesson.
Run Demonstration on stream table of high gradient V-shaped valleys.
Run Demonstration on stream table of waterfalls and headward erosion.
Give students handout on groundwater features and have them identify the different parts.
Finally, have students respond to the second Reflection Journal page.