EE 105 Lecture 8: Rivers and Floods

This set of flashcards covers key concepts related to rivers and floods, focusing on the water cycle, river dynamics, and flood management.

The Water Cycle

The continuous movement of water on, above, and below the surface of the Earth.

Freshwater

Water that has low concentrations of dissolved salts, making up about 2.5% of the Earth's water.

Floodplain

Flat land adjacent to a river that is prone to flooding.

Discharge

The flow of water that passes a cross-section of a stream, typically measured in cubic meters per second.

Erosion

The process by which soil and rock are removed from the Earth's surface by wind or water flow.

Meanders

Curves or bends in a river or stream that develop due to erosion and sediment deposition.

Oxbow Lake

A lake formed when a meander from a river is cut off, creating a curved body of water.

Alluvial Fan

A fan-shaped deposit of sediment crossed and built up by streams.

Braided Stream

A type of river that interweaves into multiple channels as it carries a large amount of coarse sediment.

Headward Erosion

The process of erosion occurring at the source of a stream, extending its length.

Superfloods

Extreme floods that can occur more frequently than traditional 100-year flood predictions suggest.

Sediment Transport

The movement of solid particles from one location to another by fluid flow.

Levees

Natural or artificial embankments that are built alongside rivers to prevent flooding.

Coastal Erosion

The wearing away of land and the removal of beach or dune sediments by wave action, currents, tidal forces, and high winds.

Evapotranspiration

The combined process of evaporation from soil and other surfaces and transpiration from plants.

Hydrologic Cycle

The cycle of transfer of water from the atmosphere to the Earth and back through various processes such as precipitation, evaporation, and runoff.

Flash Flood

A sudden and intense flood that occurs within a short time frame, typically within six hours of heavy rainfall.

Dams

Barriers built to hold back water, creating reservoirs or preventing floods but often causing sediment buildup.

Groundwater Recharge

The process by which water from precipitation and surface water enters the ground and replenishes aquifers.

The Water Cycle

The continuous movement of water on, above, and below the surface of the Earth.

Freshwater

Water that has low concentrations of dissolved salts, making up about 2.5% of the Earth's water.

Floodplain

Flat land adjacent to a river that is prone to flooding.

Discharge

The flow of water that passes a cross-section of a stream, typically measured in cubic meters per second.

Erosion

The process by which soil and rock are removed from the Earth's surface by wind or water flow.

Meanders

Curves or bends in a river or stream that develop due to erosion and sediment deposition.

Oxbow Lake

A lake formed when a meander from a river is cut off, creating a curved body of water.

Alluvial Fan

A fan-shaped deposit of sediment crossed and built up by streams.

Braided Stream

A type of river that interweaves into multiple channels as it carries a large amount of coarse sediment.

Headward Erosion

The process of erosion occurring at the source of a stream, extending its length.

Superfloods

Extreme floods that can occur more frequently than traditional 100-year flood predictions suggest.

Sediment Transport

The movement of solid particles from one location to another by fluid flow.

Levees

Natural or artificial embankments that are built alongside rivers to prevent flooding.

Coastal Erosion

The wearing away of land and the removal of beach or dune sediments by wave action, currents, tidal forces, and high winds.

Evapotranspiration

The combined process of evaporation from soil and other surfaces and transpiration from plants.

Hydrologic Cycle

The cycle of transfer of water from the atmosphere to the Earth and back through various processes such as precipitation, evaporation, and runoff.

Flash Flood

A sudden and intense flood that occurs within a short time frame, typically within six hours of heavy rainfall.

Dams

Barriers built to hold back water, creating reservoirs or preventing floods but often causing sediment buildup.

Groundwater Recharge

The process by which water from precipitation and surface water enters the ground and replenishes aquifers.

What makes floodplains important for agriculture and ecosystems?

They are highly fertile due to periodic deposition of nutrient-rich sediments and support diverse wetland habitats, though they are prone to natural disasters.

Describe the two main features that characterize a river meander.

1. Cut Bank: The outer bend where erosion is dominant due to faster water flow. 2. Point Bar: The inner bend where sediment is deposited due to slower water flow.

How does an oxbow lake form and what is its typical geological fate?

Forms when a river meander is cut off during a flood, flow bypasses it. Over time, it typically fills with sediment and vegetation, eventually becoming a marsh or dry land.

Where are alluvial fans most commonly found?

At the base of mountain ranges or hills, especially in arid or semi-arid regions, where steep, confined streams emerge onto a broad, flat valley or plain.

What geological conditions are necessary for the formation of a braided stream?

Presence of a large supply of coarse sediment (sand, gravel), steep gradient, and highly variable water discharge, often found in glacial outwash plains or arid regions with ephemeral streams.

Deposition

The geological process in which sediments, soil, and rocks are added to a landform or landmass, occurring when the agents of erosion (wind, water, ice, gravity) lose energy and drop their transported material.

Watershed (or Drainage Basin)

An area of land where all of the water drains into the same stream, lake, or river. It encompasses all land that contributes water to a particular river system.

Runoff

The flow of water that occurs when excess stormwater, meltwater, or other sources flow over the Earth's surface. It is a major component of the water cycle.

Delta

A landform that forms from deposition of sediment carried by a river as its flow leaves its mouth and enters slower-moving or stagnant water such as an ocean, sea, estuary, lake, or reservoir.