People live in floodpalin areas because of the fertile soil, easy/cheap shipping and good fishing.
What are some benefits of flooding?
1. Maintain wetland habitat 2. It provides natural irrigation – watering the crops 3. Flooding deposits silt in the floodplains, removes salt
What are some flood hazards?
Drowning Diseases (typhoid and malaria) from mosquito breeding Water Pollution Psychological stress disorders Property damage Damage to livestock and crops
What are some countries that especially vulnerable to flooding?
Bangladesh Vietnam Netherlands
What kind of areas are subject to flooding?
Flood plains – flat ground next to rivers Coastal areas – storm tides Small basins and canyons subject to flash floods Down river from unsafe dams Low, inland shores (Great Lakes, GSL) Alluvial fans
What is a drainage basin?
A watershed. The whole region from which a particular stream collects its water.
What is the closest drainage basin?
The Provo River Drainage Basin, which we live in.
What is the Levee effect?
Levees are built to give a measure of protection and control in regards to flooding. However, people then believe the area is safe and begin to develop the land, disregarding the flood potential. Subsequent flooding does not discourage resettlement or redevelopment of the floodplain areas.
Why have recent Mississippi River floods been so catastrophic?
The floodplains are populated, leaving people and property at a great risk.
Name some flood control devices.
Levees Channel improvements (which can backfire) Flood control dams ad collecting basins Reforestation after a fire.
What are deltas?
Low, flat areas of land formed near the mouth of a stream where it enters a lake or an ocean.
What are alluvial fans?
Fan shaped deposits composed of coarse sediment that is dropped by a stream as it emerges from a mountainfront onto a flatter terrain.
Why is it dangerous to build on deltas or alluvial fans?
The chance for flooding is high.
Name the main river channel type.
Straight Meandering Braided Sinuous
Describe a meandering river.
The river does not move in one straight line, but moves back and forth in a patter. Sandbars occur on the inside bank of the meander.
Describe a braided river.
When the river divides and comes back together in multiple places.
Describe a straight river.
Rivers are not naturally straight, especially for long distances. Human make them straight in order to prevent flooding or maintain boundaries.
Describe a sinuous river.
These rivers has a very gentle bend in them. They are similar to a meander, but not as drastic.
How do dams alter rivers and impact flood potential?
Dams alter the path and flow of the river. By damming the water, we can generate energy and control the flooding. However, dams put a lot of weight on the earth, seal off areas previously available, and dry out some parts of the original river areas.
What is problematic about straightening river channels?
Rivers do not naturally run in a straight line. Over time, they will try to move to regain their natural flow that includes bending.
What is a 10 year vs a 100 year flood?
A one-hundred-year flood is calculated to be the level of flood water expected to be equaled or exceeded every 100 years on average. Similarly, a flood level expected to be equaled or exceeded every 10 years on average is known as a ten-year flood.
What is discharge?
The amount of water moving through a cross section of a river per unit of time.
What is sediment load?
The amount of sediment carried in the water.
Flash flood vs downstream flood
Flash floods are very isolated whereas downstream floods are prolonged precipitation over a greater area.
What is the National Flood Insurance Program?
Flood insurance program provided by the Federal Government. The program provides short-term financial aid to victims of floods and establishes long-term land use regulations for the nations floodplains.
What is the cost of landslide prevention?
The benefit to cost ratio is $10 dollar to prevent $2,000 damage caused. Thistle, UT Landslide caused $400 Million in damages, but could have been prevented for $400,000.
What do avalanche paths look like in the summer?
Trees broken and cleared, debris everywhere. Destroyed vegetation easily marks the tracks.
What is Hawaii’s Hilina slump?
A 4,760 cubic mile chunk of the Big Island (Hawaii) is breaking away at the rate of 4 inches per year. This is the Hilina Slump, and it is said to be “the most rapidly moving tract of ground on Earth for its size.” The Hilina Slump can move much faster. At 4:48 AM, November 29, 1975, a 37-mile-wide section suddenly dropped 11? feet and slid seaward 26 feet. The result was a magnitude-7.2 quake and a 48-foot-high tsunami. This was a minor of the slump. If the entire 4,760-cubic-mile block decided to break off, it would probably create a magnitude-9 quake and a tsunami 1,000-feet high. All the coast-hugging cities of the Hawaiian Islands would be swept away. And LOOK OUT Australia, Japan, and California.
How does insurance and disaster aid impact development of slide-prone areas?
By providing insurance, buyers are more comfortable purchasing a home in a hazard-prone area. Unavailability of ins can discourage unsafe development. Disaster aid is minimal due to limited losses.
Important factors influencing slope failures.
1. Saturation of slope material with water. 2. Earthquakes 3. Freezing and thawing
Why is soil subsidence a problem?
-Subsidence results in irregular patterns of ground failure -Damages roads, buildings, gas lines, water pipes, etc -Aquifers can’t recharge due to sediment compaction -Loss of land in coastal areas (Louisiana)
the Karst process
-The dissolving of limestone by (weak carbonic acid) groundwater
Landforms produced through the karsting process.
Sinkholes Speleotherm Haystack Hills Tufa cones
Types of rock dissolved in groundwater.
Freshwater: rock salt, rock gypsum Acidic water: Limestone, dolostone, marble
The sequence of the karsting process
Water seeps into the ground through cracks, dissolving limestone as it goes. The water stops at shale, as it does not dissolve it. As large caverns are dissolved away by groundwater, the topsoil collapses.
What is thermokarst?
The subsidence of permafrost as the topsoil defrosts in summer and the freezes in winter.
What is the coriolis effect?
Something traveling over the earth appears to move to the right on its trajectory because the earth is rotating underneath it. In southern hemisphere everything turns to the left. There is no coriolis effect on the hemisphere.
What are fronts?
Air masses between dissimilar air masses. Cold fronts push in, warm fronts don’t move much.
What is the Fujita scale?
A scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation.
Different forms of severe weather
Thunderstorms Tornadoes Hurricanes Fog Drought
Characteristics of thunderstorms
They are produced mostly by convection as the air over warm areas rises. They are most common in the tropics because of heat and humidity. Rare or absent poleward of 60 degrees. Often produces hail (small in Utah) Heavy rain kills the storm
What makes thunderstorms dangerous
Where do most tornadoes occur?
In the United States
Conditions that produce tornadoes.
Warm, humid air from the south and cool, dry air from the north.
What is wind shear?
When the air up high is moving faster than the air below.
Characteristics of tornadoes.
They occur within a frontal storm along a cold front. They have the strongest of any kind of winds, 60 to 260 mph. May last few seconds to a few hours. they have a small path of destruction, travel 30-60 mph.
What makes tornadoes dangerous?
-The largest, most destructive storms are 100-600 miles in diameter -Often produce a storm surge -Often follow the trade winds
Describe the eye of a hurricane.
10-25 miles in diamter Calm, because air is subsiding in the middle
Where do hurricanes get their energy?
They get energy from warm water. When they hit land or cold air, they die quickly.
Requirement to produce hurricanes.
Ocean water 80 degrees or higher, 150 feet or deeper. Coriolis effect (which means none start at equator) Converging winds
Tropical disturbance Tropical depression – winds less than 39 mph, small area of low pressure, gently rising air Tropical storm-sustained winds of 39-73 mph. Hurricane
Oceans with the most hurricanes
Pacific – 24 per year Indian and Atlantic tied at 6 per year
Other names for hurricanes.
What is fog?
A cloud on the ground.
Circumstances that create fog.
The air near the ground chills to the dew point temperature. The dew point varies based on the level of humidity in an area, but is the temperature at which water vapor condenses.
When is fog hazardous?
When is obscures visibility for travel.
What are the foggiest places on earth?
Pacific Coast New England Appalachian Mountains
Why is drought called the creeping hazard?
It takes weeks to feel. The effects are felt very gradually.
What is drought?
An unusual dry period that results in a shortage of water.
Desertification. Excess pressure on the land from excess cattle
Physical causes of drought
Teleconnections, linkages to distant climatic anomalies. Like El Nino or La Nina; cold sea temps which produce dry winds.
El nino/la nina
Equatorial, eastern pacific sea temps get warm, producing hurricanes. La nina-east pacific becomes cool, producing dry wind.
Famine and drought
Famine is connected to drought, but the following factors make it worse: Poverty Malnutrition Environmental degradation Poor governance
Protection against drought.
Cloud seeding Water projects: wells and irrigation vs salinization
Can cause many deaths. Chicago has record numbers for deaths.
Desertification in Africa
Pastoralists followed the rain with their animals. Now, country boundaries prevent them from traveling as they did and animals are overgrazing in the areas where they are stuck. International aid goes to farmers, not pastoralists.
Adjustments and adaptation to severe weather.
Hazard resistant shelters Tornado shelters Escape platforms Breakwaters Homes on stilts Strict building codes Insurance
Why was Hurricane Katrina so disastrous?
-Substantial portions of land below sea level -Coastal areas populated by people who had never experienced a hurricane -Levee construction resulted in lost barrier island that would have mitigated the effects -New Orleans has subsided due to groundwater pumping, accumulated sediment discharge weighing down the earth and the levees and pumping systems were over 100 years old.
Local change in sea level due to the height of the land relative to the sea
Eustatic sea level change
global change in sea level due to changes in density or mass
Barrier islands are formed by
An accumulation of sand that acts as a barrier to ocean waves. The gradually build upon an existing sandbar
Human structures along the coasts that are supposed to reduce erosion
The combination of the the back and forth movement of waves on the beach and the longshore drift carrying sediment parallel to the shore. The result is that the wave hit the shore at an angle. In th eUS, littoral transport generally moves to the south.