EAS 205 - Floods

Flood

An overflow of water that submerges land that is usually dry.

Hydrology

The study of floods and their impact.

Types of Floods

River Floods, Coastal Floods, Storm Surges, Inland Flooding, and Flash Floods.

Hydrologic Cycle

The cycle where water moves from the atmosphere to the earth's surface and back to the ocean.

Discharge

The volume of water passing a point in a given time through a channel, measured in m³/s.

Sediment load

Material temporarily or permanently suspended in a flow.

Capacity

Total sediment load carried by a flow, related to discharge.

Competence

A flow's ability to carry material of a given particle size.

Gradient

The steepness of a stream's channel.

Base level

The lowest elevation to which a stream can flow.

Graded stream

A stream where the profile has become stable and experiences neither erosion nor sedimentation.

Braided Stream

A stream that constantly breaks apart and comes together, usually steep with high sediment loads.

Meandering Stream

A stream that occurs on gentle gradients, eroding unconsolidated sediments.

Floodplain

A flat area about level with the top of the channel that floods when the stream spills over its banks.

Natural levees

Ridges of coarse material that confine a stream within its banks between floods.

Hydrograph

A plot of stream discharge at a point over time.

Flash flood

A rapid rise in stream stage characterized as a type of upstream flood.

Hydrographs: Upstream vs Downstream

Upstream floods are localized, while downstream floods occur in larger drainage basins.

Stormwater Management Pond (SWM)

Ponds designed to manage stormwater runoff and reduce flooding risk.

Flood Frequency Curve

Graph representing the recurrence interval of floods.

Recurrence interval formula

R = (N + 1) / M, where R is the recurrence interval, N is the number of years, and M is the ranking of annual maxima.

Drought

A prolonged dry period that impacts water availability in a region.

Flood Characteristics - Stage

The elevation of water in a stream.

Saffir-Simpson Wind Scale

Categorizes hurricanes based on sustained wind speed.

Eustatic Sea Level

Distance from the center of the earth to the sea surface.

Relative Sea Level

Sea level observed with respect to land.

Emergent Coastlines

Coastlines formed from tectonic uplift or a fall in sea level.

Submergent Coasts

Coastlines permanently flooded due to a relative rise in ocean water.

Wave-cut platform

Flat area at the base of a cliff eroded by waves, can form caves.

Tides

The rise and fall of sea level caused by gravitational forces from the moon and sun.

Wave Energy

Energy of the wave proportional to the square of wave height.

Longshore Drift

Sediment transport parallel to the shoreline due to wave action.

Hurricanes

Storms forming over warm ocean waters and classified by wind speed.

Tropical Cyclones

Storms in the South Pacific or Indian Ocean equivalent to hurricanes.

Typhoons

Storms occurring in the Northwestern Pacific Ocean, similar to hurricanes.

Mitigation for Flooding

Includes zoning regulations, flood barriers, and natural defenses.

Mangroves

Trees that trap sediment and protect coastlines from erosion.

Catastrophism

The theory that Earth's features were shaped by rapid, violent events.

Uniformitarianism

The principle that present geological processes are the key to understanding the past.

Channeled Scablands

Landscape in Washington, a product of ancient, extreme flooding.

Jökulhlaup

A glacial outburst flood occurring rapidly due to melting ice.

Erratics

Large boulders left by glaciers, found far from their original location.

Rhythmites

Sedimentary deposits indicating repeated flood events.

Geological Fingerprints

Features left behind by massive flooding events, showing evidence of past catastrophes.

Glacial Lake Missoula

A glacial lake that existed over 15,000 years ago, responsible for significant flood erosion.

Zanclean Flood

A rapid refill of the Mediterranean Sea after it was disconnected from the oceans.

Strontium Isotopes

Used as paleoclimate proxies, providing evidence of past sea level changes.

Flood Control Dams

Structures built across rivers to manage water flow and reduce flooding.

Storm Surges

Rise in sea level associated with strong winds from storms.

Upstream Floods

Floods localized in a small upper part of a drainage basin.

Downstream Floods

Floods occurring in larger, lower parts of a drainage basin.