Geology Chapter 6 Study Guide

They are generally produced by intense rainfall of short duration over a relatively small area.

In what type of climate do most natural flash floods occur?

Gradient is the slope of a river. It is shown on a longitudinal profile. Gradient is rise over run.

Gradient

We covered the surfaces so it can't absorb rainfall.

How do humans impact the dynamic equilibrium of a stream?

helps us know where the 20 year flood and 100 year flood in planning construction

How does flood hazard mapping contribute to reducing the effects of flooding on humans?

Injury and loss of life Damage caused by currents, debris and sediment to farms, homes, buildings, railroads, bridges, and roads. Erosion and deposition of sediment related to loss of soil and vegetation

Primary effects of floods

Short-term river pollution of rivers Hunger and Disease Homelessness

SecondaryShort-term river pollution of rivers -Hunger and Disease -Homelessness effects of floods

Is land surface and waters (rivers and streams) that drain into a particular body of water such as a river, a lake, a wetland, or an ocean. The Basin acts like a funnel.

Understand and be able to define the meaning of the terms drainage basin and watershed. (They are the same thing)

Cut banks: The fast-moving water erodes the riverbank on the outside of the bend to form a steep or near-vertical slope. Point Bars: Slower water on the inside of a meander bend deposits sand and sometimes gravel.

Understand how cut banks and point bars are made.

Caused by intense rainfall of short duration over a relatively small area. Both natural and human induced

Understand the causes of flash floods and which are natural and which are human-induced.

-Primary effect of Hurricanes -Flooding due to Hurricane Sandy -Secondary effect of earthquakes and landslides -Fires -Produce shorts in electrical circuits and erode and break natural gas mains -Cause of coastal erosion

Understand the linkages of flooding with other natural hazards.

-Drainage affects plants/animals -cutting trees=no shade destroys habitats -changes diversity of flow patterns for aquatic life -degrades the aesthic

What are the drawbacks of using channelization to control flooding?

Amount and distribution of precipitation in drainage basin. Rate at which the precipitation soaks into earth. How quickly surface runoff reaches river. Amount of moisture in the soil.

What are the four factors that combine to cause river flooding?

Headwater of a stream/river is the steep at high elevation

What are the headwaters of a stream/river?

Erosion, transport, and deposition

What are the three parts of the total sediment load of a stream/river?

on average every 100 years, you have a 1% chance that it will happen every year.

What does the term "100 year flood" mean? (It means that there is a 1 in 100 chance of a flood of this magnitude happening every year.)

They are not above sea level, every year they go up a little bit. Soon sea level will reach Bangladesh and flood them.

What factor other than river bank overflow is going to cause flooding in the near future in Bangladesh?

A triangular or irregularly shaped deposit, if it extends into a larger body of water. It forms at the mouth of a river.

What is a delta and where do they form?

Area bordering a river channel that has the potential to flood; it is made by flooding.

What is a floodplain and how is it made?

Natural levees are formed by its river in its process of flooding. A natural levee is formed by a deposit of sand or mud built up along, and sloping away from, either side of the flood plain of a river or stream. This is done by the action of the water itself. The process occurs slowly over a number of year.

What is a natural levee and how is it made?

The river commonly forms a fan-shaped deposit on land. Formed where a stream leaves a canyon and expands outward into Death Valley.

What is an alluvial fan and where do they form?

Upstream Floods are caused by intense rainfall of short duration over a relatively small area. Downstream Floods are caused by storms of long duration that saturate the solid and produce increased runoff.

What is the major difference between an upstream and a downstream flood?

40%

What percentage of deaths in hurricanes come from drowning?

A stream that is sinuous. They develop in areas with low gradients (lower energy than braided streams). Steep areas

Where do meandering streams form - in steep or flat areas?

Slope, gravity is being pulled down on it.

Where is a stream's overall downstream flow energy the highest - on a slope, or on flat ground?

The deepest part of the channel

Where is the velocity of the water, and hence the energy, of a meandering stream the highest?

-Land use changes can affect that equilibrium -Forest to farming creates more erosion and sediment -Sediment will build up the gradient of the stream -Stream will flow faster until it can carry greater amount of sediment -Increases magnitude and frequency of floods -Urban areas have impervious cover and greater storm sewers -Carries water to stream channels more quickly causes flashy discharge-rapid rise and fall of flood water -Bridges block debris creating dams and flash flooding

Why do we build human-made levees?

Levees are good at protecting bits of land and communities where we've deemed it unacceptable that they be exposed to repeated floods.

Why is the Mississippi River watershed so prone to flooding?

1) Levees failed 2) Houses weren't build strong enough

According to the movie Katrina: The Storm That Drowned a City: What were the two main causes of the flooding of New Orleans due to Hurricane Katrina?

Lowest elevation of river.

Base level

A stream that has many bar deposits. Braided streams are wide, shallow, and heavily loaded with sediment. Braided streams are characteristic of deserts and mountainous regions where sand and gravel are abundant.

Be able to recognize a description of a braided stream and understand the conditions under which they form.

Reservoirs: Large natural or artificial lake used as a source of water supply. Ocean is the largest pool. Important processes in hydrologic cycle: Transpiration and evaporation

Be able to recognize the reservoirs, or pools, and the processes on a diagram of the hydrologic cycle.

Fertile Lands Aquatic ecosystems Sediment supply Urbanization increases magnitude and frequency of floods in small urban areas because of high percentage of impervious cover (roads, roofs, etc.).

Name three natural service functions of flooding. In what two significant ways does urbanization increase the magnitude and frequency of floods?