Flooding Flashcards
Define: Flood
An overflow of water that submerges land that is usually dry
What is a stream?
a body of water confined to a channel that feed into rivers
What is a river?
the major branch of a stream system
What is a drainage basin? What separates them?
the area of land from which a stream or river collects its water
topographical features divide basins (natural barriers)
What is the hydrological cycle’s main components, with a brief description?
- Evaporation - water turning to vapour
- Condensation - condensing of water vapour in clouds
- Precipitation - water falling back to earth
- infiltration - water soaking into the ground
- runoff- water that does not infiltrate
- groundwater - water that is deeply infiltrated that will refill rivers/streams
Define: discharge
The volume of water that flows through a river or stream at a specific point
What is discharge a function of
width x depth x flow velocity
What is sediment
All the material temporarily or permenatly suspended in the flow
What is a hydrograph? What does it tell us?
a plot of stream discharge at a point over time
lets us monitor stream outflow to predict flooding
What is capacity?
total sediment load carried by a flow
What is compentence?
the flows ability to carry material of a given particle size
What is base level?
the lowest level elevation to which a stream flows
What is gradient?
the steepness of a streams channel (elevation change)
What characterizes a braided stream
multiple channels split apart and join together
at high elevations
What characterizes a meandering stream?
winding, loop like bending of the chanel
low elevations
What is a floodplain?
A flat area, level with the top of the channel that floods when the stream fills over its banks
what are natural levees?
ridges of course material that build up on its banks confining floodwaters
Define: Downstream flood
floods that affect the larger portion of the drainage basin
Define: stage
the height of the water surface at a given location
Define: Upstream flood
occurs in small localized areas of the upper drainage basin
Define: Crest
the highest point or maximum elevation reached by water in a river/stream during a flood
Define: Flash flood
a sudden upstream flood that occurs in a short period of time
What is a flood frequency curve? what is its function?
graphical representation of past floods and their magnitude
tells us the likelihood that a similar flood will occur again
What is surface runoff affected by? why?
- ground cover - diff materials absorb more than others
- topography - shallow slope infiltrates more than steep slopes
- vegetation - plants absrob water reducing runnoff
- climate - rainfall, spring runoff, etc.
What human actions influence floods? (3)
- urban development
- Deforestation
- climate change
How does urban development impact flooding
less natural ground cover and vegetation reducing infiltration and increasing runoff
How does deforestation impact flooding?
there are less trees/plants to absorb water reducing infiltration and increasing runoff
How does climate change impact flooding?
increased rainfall, rising sea levels, glacial melting
What is restrictive zoning?
avoiding building in designated zones to reduce flood risk
What is a retention pond?
a man-made pond that captures and slowly releases storm water
What is a diversion channel?
channel built to redirect floodwaters to vulnerable areas
What is chanellization?
modification of river channels to improve flow and reduce flooding
What are levees?
natural or man made riverbank barriers to maintain floodwaters
What are flood controlled dams & reservioirs?
structures that store excess water and release it gradually
What is the biggest river flood mitigation technique?
not building on floodplains
Describe the Edmonton flood of 1915
big flood that changed the development of urban areas in edmontons river valley
Describe the 2013 Calgary flood
big flood due to heavy rains that resulted in the lowering of water levels in dams
Explain the principle of catastrophism
geological principle that states earths landscapes are shaped by sudden, short lived, intense events
Explain the principle of uniformitarianism
geological principle that states earths landscapes are shaped by continuous and uniform processes over long periods of time
Explain the principle of catastrophic uniformitarianism
geological principle that states earths landscapes are shaped by both long and continuous processes and short intense events
What does the bedding type tell us about flood deposits?
the sedimentary characteristics tell us about the presents of floods and their characteristics
What are humans proximity to the coast?
40-90% of people live within 5km of the coast
pop density is much higher in coastal areas vs inland
How do tectonics impact coastline characteristics?
differences in tectonic activity lead to vaired coastal landscapes
Define: active margin
where tectonic plates are activly moving and interacting
Explain a subduction zone and what kind of coastline it results in
when a oceanic plate slides beneath a continental plate causing uplifting
results in cliffs and rugged coastlines
Define: passive margin
where tectonic plate activity is minimal, not where plates meet
Explain what kinds of coast lines arise from passive margins
slight pushing of the oceanic plate on continental but no significant subduction
results in coastlines with long continental shelves and sandy beaches with gentle slope
How does the materials of the coastline impact its characteristics?
impacts its resistance to erosion and the presence of different coastal features
Explain how waves and energy affect coastal appearance
high energy environments result in more erosion, where as low energy environments have more sediment build up
Define: relative sea level
the height of the sea level in relation to the land
- results from land masses and sea level rising/falling
Explain what a emergent coastline is
when land rises or sea level falls decreasing relative sea level
results in wave-cut platforms
Explain what a submergent coastline is
when land sinks or sea level rises increasing relative sea level
- results in drowned valleys
How are waves formed?
via wind speed and fetch
Explain wave movement as it approaches the shore
wave moves in circular motion, closer to the shore it turns into a ellipses shape before the wave breaks
Explain how sediment moves along a shoreline
longshore currents and wave motion move sediment parallell to the coast
Define: Sediment budget
how much sediment comes into an area minus how much sediment is exported out by the ocean
What sediment conditions result in a eroding shoreline?
more sediment out than in
What sediment conditions result in a built-up shoreline
more sediment in than out
What is a groin? its function?
build to prevent beach erosion by trapping sediment by building barriers perpendicular to the shoreline
What is a jetty? its function?
built to keep open channels and harbour entrances from sediment deposition
Why did Bayocean fail?
because of the building of a jetty upstream, resulting in erosion downstream
describe the foreshore
intertidal zone that is exposed between low and high tide
describe the offshore
subtidal zone, with a lower gradient, not affected by waves, completely underwater
Describe the backshore
supratidal zone not usually affected by water, formation of sand dunes
describe the shoreface
subtidal zone, steep gradient, heavily influenced by waves, sediment in motion
Briefly explain the origin of tides
via the gravitational pull of the sun (30%) and the moon (70%)
What is storm surge?
abnormal rise in sea level caused by strong winds and low atmospheric pressure from storms
What are the conditions required for a tropical cyclone
- warm ocean water
- low pressure
- coriolis effect causing air to spin
- continuous energy supply
How does coriolis effect determine hurricane trajectories
causes cyclone trajectories to curve rather than move in a straight line
What are the consequences of storm surge
coastal flooding, coast erosion, destruction of infrastructure and ecosystems
How does climate change affect hurricanes
increased sea level, surface temperature, and precipitation will result in more intense hurricanes more often with greater damage
briefly explain how hurricanes are present in the rock record?
hurricanes imprint the sedimentary rock record via coarse sediment deposits and fossils
Describe the western interior seaway
a shallow inland sea that connected from the gulf of mexico to the arctic ocean
marine environment in alberta
Describe Amadeus Grabau pulsation theory
discovered via rock deposits and fossils that earths features are due to the rythmic rise and fall of sea level
Explain what cratonic sequences are
large-scale, regional sedimentary deposits that occur on stable continental crust,
describe Jospeh Barrell cycles theory
discovered via sedimentary rock that sea level rises in cyclicity rhythms affecting rates of sedimentation
Explain what happened in the messinian event during the messinian period
mediterranean sea disconnected form oceans causing water to evaporate leaving behind salt deposits
Explain what happened in the messinian event during the zanclean period
atlantic ocean water found a path through the gibraltar strait filling the mediterranean sea
initially slow then very fast filling
explain the differences in filling between the western and eastern mediterranean
filled at different rates due to topography acting as a barrier (sicily sill)
What do the seismic section of the channel tell us?
tell us that there was 600m of erosion along the mediterranian seabed from rapid water flow
How does the geological record explain sediment transport during the messinian flood
the flood transported 40 billion cubic meters of sediment within the channel
