Water Erosion and Deposition Chapter 9 Water Erosion and Deposition

Factors affecting runoff: Amount of rain Length of time rain falls Surface Water Runoff – water that doesn't soak into the ground or evaporate but instead flows across Earth's surface. Factors affecting runoff: Amount of rain Length of time rain falls Ex: light rain falling over several hours will have time to soak into the ground while heavy rain falling within an hour will run off because it cannot soak in fast enough. Steepness of slope Vegetation

Rill erosion – begins when a small stream forms during a heavy rain. Water Erosion Rill erosion – begins when a small stream forms during a heavy rain. Water moving down the same path creates a groove called a channel. Gully erosion – when a rill channel becomes broader and deeper. Sheet erosion – when water erodes without being in a channel. This occurs when water that is flowing in sheets picks up and carries away sediments. Ex: how water flows off the hood of a car. Stream erosion – takes place when water continues to flow along a low place it has formed. As water moves along it picks up sediments from the bottom and sides of the channel...this process makes the stream deeper and wider.

All water in a river system eventually flow to one location. River Systems – water that comes from rills, gullies and smaller streams join together to form larger streams. Larger streams come together to form rivers. Rivers grow and carry more water as more streams join. Drainage Basins – the area of land from which a stream or river collects runoff. All water in a river system eventually flow to one location.

Stages of Stream Development Pg. 244 Young Stream – a stream that flows quickly through a steep valley. Bottom of stream erodes quicker than sides because of high level of energy. Often has waterfalls or white water rapids. Mature Stream – a stream that flows smoothly through its valley. Sides of stream erode causing curves to appear. Curves turn into a broad arc called a meander. The broad, flat valley floor formed by a meandering stream is called a floodplain. When a stream floods, it will often cover part or all of the floodplain. Old Stream – flows smoothly through a broad flat floodplain that it has deposited.

Too Much Water FLOODS!!!! Water needs to go somewhere when there's too much of it. Dams and levees are built in an attempt to prevent flooding. Deposition of Surface Water Some stream sediment is carried only a short distance...sediment is often deposited within the stream channel itself. Deltas – sediment that is deposited as water empties into an ocean or lake that forms a triangular, or fan-shaped deposit. Alluvial fan – when the river waters empty into a mountain valley onto an open plain.

Groundwater Groundwater – water that soaks into the ground collects in cracks and empty spaces. The groundwater system has connecting pores (much like how streams connect to rivers). Permeable – if water can pass through materials (sandstone) Impermeable – if water cannot pass through materials (clay or granite) Aquifer – a layer of permeable rock that lets water move freely Water table – the upper surface where all of the pores are filled.

Water Table Wells – extends deep into the zone of saturation, past the top of the water table. Groundwater flows into the well and a pump brings it to the surface. Springs – forms when the water table meets Earth's surface; often found on hillsides and used as a fresh water source. Geyser – a hot spring that erupts periodically, shooting water and steam into the air. Groundwater is heated to high temperatures, causing water to expand underground. Cave formation – groundwater dissolves limestone to make caves and also deposits inside caves. Sinkholes – form when underground rock is dissolved near the surface.

Ocean Shoreline * Where land meets the ocean. Rocky Shorelines – rocks and cliffs. Sediments in the water grind against the cliffs, slowly wearing the rock away. Soft rocks become eroded before harder rocks do, leaving islands of harder rocks. Sandy Beaches – deposits of sediment that are parallel to the shore. Smooth, gently sloping shorelines.

Sand Erosion and Deposition Longshore Currents (water that runs parallel to the shoreline) carry sand along beaches to form features like islands, spits and sandbars. Storms and wind also move the sand. Beaches are damaged easily by storms and human activities. Barrier Islands – sand deposits that are parallel to the shore but are separated from the mainland.