Chapter 2 Section 1 Streams and Rivers How Do Rivers Begin? Rivers begin as trickles of waterthat run over the ground and join together in larger streams. Rain that falls can Evaporate immediately Soak into the soil as groundwater Form runoff (water that flows over the ground surface) that can eventually lead to a river. Rain that falls ? Time to review! Time to review! Evaporate immediately Rain that falls
Soak into the soil as groundwater Form runoff Time to review! Factors That Affect Runoff
The nature of the ground surface (water passes through soil easier than cement, so grass/plants will slow water down as it is absorbed) The rate of rainfall (a lot of rain cant all soak in, so some becomes runoff) Whether the land is flat or hilly (water falls faster down a steep slope than over flat ground, so the water moves too fast to be absorbed and forms a stream instead) River Systems The smaller streams and rivers that feed into a main river are called tributaries. A river system is made of the main river and all of its tributaries. Watersheds The land area that supplies water to a river system is called a watershed or drainage basin. The Clinton River Watershed, which ends at Lake St. Clair is the nearest major watershed. However, the Great Lakes Watershed also impacts us as well. * technically Grosse Pointe is considered direct drainage which means we drain directly into Lake St. Clair and not into a watershed Watersheds One watershed is separated by another by a ridge of land called a divide, and streams flow in different directions on each side. New Vocabulary Words River Systems: Runoff Tributary River system
Watershed Divide Rivers Shape the Land Erosion is the process during which fragments of soil and rock are broken off from the ground surface and carried away. Rivers Shape the Land Deposition the process during which soil and rock are left behind and build up. How do rivers shape the land?
Rivers wear away landforms through erosion and build new landforms through deposition. With erosion, sediment is carried away. Soil and rock are left behind with deposition. New terms: erosion and deposition Rivers Shape the Land Rivers wear away landforms through erosion and build new landforms through depositions. The particles of rock and soil that are picked up and moved by erosion and deposition are called sediments. Rivers Shape the Land The faster the water flows, the more energy it has to move heavier sediments. Three factors affect a rivers speed: The steepness of the slope (steeper = faster) The amount of water in the river (more = faster) The shape of the channel (deeper/broader = faster) How fast is that river? Time to Review! Factors affecting
the speed of a river ? How fast is that river? Time to Review! Factors affecting
the speed of a river The steepness of the slope The amount of water in the river The shape of the channel Profile of a River The many small streams that come together at the source of the river are called the headwaters (usually fast, choppy, and narrow). Profile of a River Downriver, the channel becomes deeper and wider due to erosion, it is less steep, has more water in it from tributaries, and continues to move swiftly but much more smoothly. The Flood Plain The broad, flat valley (created by years of erosion) through which the river flows is called the flood plain. Profile of a River Small obstacles in the rivers channel cause the water to flow slightly to one side or the other, creating a bend in the river. Profile of a River The process of eroding and depositing sediments on the curves of a river channel will gradually form loops called meanders. Profile of a River https://www.youtube.com/watch?v=4qKS_Nk7UmY
The crescent-shaped, cutoff body of water that remains after a river breaks through the ends of a meander is called an oxbow lake. https://www.youtube.com/watch?v=4qKS_Nk7UmY Profile of a River The mouth is the point where a river flows into another body of water (a larger river, a lake, or an ocean). Use the diagram below to answer #14 - #18: Profile of a River Profile of a River When the river hits the larger body of water at the mouth, it instantly slows down. This slow speed allows most of the rivers sedimentto be deposited and build up at the rivers mouth, in an area called a delta. Profile of a River New Vocabulary Words Profiles of a River Headwaters Flood plain
Meanders Oxbow lake Mouth Delta Rivers and Floods A flood occurs when the volume of water in a river increases so much that the river overflows its channel. Precipitation can add more and more water to a river, making it faster and stronger. Can Floods Be Controlled?
A dam is a barrier across a river that may redirect the flow of the river to other channels or store the water in an artificial lake. Fear or welcome a flood? Yeah flood!!!
Deposition leaves a layer of nutrient rich sediment behind. Boo flood! Destroy farms and crops Destroy homes Loss of electricity, transportation, clean water Injury or death of people and livestock Can Floods Be Controlled?
Levees are long ridges formed by deposits of sediments alongside a river channel. Man-made levees are also used to make natural levees stronger. Can Floods Be Controlled?
When Hurricane Katrina hit New Orleans, Louisiana in 2005, some of the levees broke and flooded large areas of the city. When does a flood occur? A flood occurs when the volume of water in a river increases so much that the river overflows its channel. https://www.youtube.com/watch?v=RNde3bnXaVM Fear or welcome a flood? Yeah flood!!!
Deposition leaves a layer of nutrient rich sediment behind. Boo flood! Destroy farms and crops Destroy homes Loss of electricity, transportation, clean water Injury or death of people and livestock How can we control floods?
Build a dam a barrier across a river that may redirect the flow of a river to other channels OR store the water in an artificial lake. Levees can be natural or people made.People can build up a natural levee with sandbags. Vocabulary Words: dam and levee https://www.youtube.com/watch?v=oD4QHkN57FM