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the maximum clast size transported
the total quantity of sediment carried
- Decrease in water velocity affects sediment transport
- Competence reduced, sediment drops out.
- Boulders, then gravels, then sands fill channel bottoms.
- Sands form inside banks (point bars).
- Silts and clays drape floodplains.
- Stream flow begins as scattered _______
- Water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land.
Dendritic Drainage Pattern
- Branching or tree-like
- Common in regions of uniform material
Radial Drainage Pattern
- Draining in all directions away from a point
- Found at the perimeter of a high region or feature(mesa, peak, or mountain, etc.)
Rectangular Drainage Pattern
- Channels aligned primarily in two directions
- Common in gently sloped areas of orthogonally jointed rocks
Trellis Drainage Pattern
- Trunk stream flows through resistant rocks,tributaries flow between ridges
- Common where surface alternates between erodible and resistant materials
Parallel Drainage Pattern
- Several streams with parallel courses
- Common in surface with uniform slope
- Area of land that drains into a stream
- Land areas drain into a trunk stream or body of water
- The amount of water flowing in a channel
- Volume of water passing a point per unit of time
- Multiply cross-sectional area x average water velocity
- D = Ac x va
- The energy of flowing water is from mass and gravity
- Streams convert potential energy (PE) to kinetic energy(KE). KE (e.g., fast water flow) lifts and moves solids
the“sandblasting” of rock by particles in fast moving water
- Larger particles roll, slide, and bounce along the bottom
- Moves by saltation.
Fine particles (silt and clay) in the water
- Movement of solid particles
- High discharge—Large cobbles and boulders may move.
- Low discharge—Large clasts are not moved.
Change in elevation per distance flowed
The lowest point to which a stream can erode
- Velocity drops to zero when it reaches base level.
- Ultimate base level is sea level.
- A lake is a local or temporary base level.
- A ledge of resistant rock may define temporary base level
Valleys and Canyons / Base Level Rises
Stream flow slows, and the valley become filled with more sediment.
Valleys and Canyons / Base Level Falls
Stream flow quickens, and the incision of channels may leave stranded terraces.
- Gradient is so steep that water cascades or free falls.
- Scours a deep plunge pool.
- Basal erosion leads to collapse of overlying rocks.
- Temporary base levels.
- Trunk stream consists of many interfingering channels
- Sediment load is very high and channel is very shallow
- Abundant coarse sediment moves during floods.
- Sediment is deposited, chokes channel in normal flow.
- Weaving channels create ephemeral sand and gravel bars.
- The channel is modified during periods of flood
- Fast part of current swings back and forth
- Momentum increases during flood, erodes outside bank
- Forms when a stream enters standing water.
- Stream divides into a fan of distributaries.
- Velocity slows; sediment drops out.
- One stream captures the flow of another.
- A stream with vigorous headward erosion and steeper gradient intercepts a stream with gentler gradient.
- The captured stream flows into the new stream.
- Tectonic uplift may raise a region that has an entrenched stream.
- If erosion keeps pace with uplift, the stream remains in its channel.
- If the rate of uplift exceeds erosion by the stream, drainage changes.
Evaluating Flood Hazards
A 100-year flood means 1% risk of such a flood in 1 year.
- Groundwater resides in subsurface pore spaces.
- Pores are open spaces within any sediment or rock.
- The total volume of open space.
- Geologic materials exhibit a wide range of porosities.
- Originally formed with the material.
- Voids in sediment
- Vesicles in basalt
- Open-reef framework
- Develops later
- The ease of water flow due to pore interconnectedness.
- Highly _____ material allows water to flow readily.
Sediment or rock that transmits water easily.
Impermeable or low permeability sediment or rock that hinders water flow.
- An aquifer that intersects the surface
- In contact with the atmosphere
- Easily contaminated
- An aquifer beneath an aquitard
- Isolated from the surface
- Less susceptible to pollution
Above the water table, pores are mostly filled with.
Below the water table, pores are filled with water
- Specific measurement of liquid pressure above a geodetic datum
- Measured by piezometer
Determined by measuring the hydraulic head. Flow always moves from a high to a low hydraulic head
Groundwater Flow / Recharge Areas
Groundwater infiltrates through _____ areas
Groundwater Flow / Discharge Areas
Groundwater exits the substance through ____ area.
An equation that predicts the volume of water passing through an area of an aquifer at any given time
Q = KA(h1 – h2)/j
- Q = Discharge volume (m3/day).
- K = Hydraulic conductivity (m/day).
- (h1 – h2)/j = Hydraulic gradient (m/m or dimensionless).
- A = Cross-sectional area perpendicular to flow (m2).
Natural groundwater outlets
Cone of Depression
- A downward-pointed conical-shaped surface
- Steepest near the well; flattens with distance
- The cone may expand outward with continued pumping
- A small well creates a small cone.
- A large well creates a large cone.
- Water is heated to the boiling point in a vertical spring.
- Pressure exerted by the water column prevents boiling.
- Some water escapes and pressure is reduced.
- The water boils, turns to steam, and erupts as a geyser.
- The cycle repeats after the emptied chamber is refilled
- Water in pore space holds grains apart.
- When groundwater is removed:
- Sediment grains compress; pore spaces collapse.
- The land surface cracks and sinks.
Failing Septic Systems
- Should effectively accept liquid wastes from your house and prevent biological and nutrient contaminants from getting into your well or nearby lakes and streams.
- Any, time these things do not happen, the system is failing.
- Most remedial strategies include removing the source.
- Pump and treat.
- Volatilize and vaporize.
- Steam clean.
Utilizes bacteria to clean groundwater
Develop when groundwater dissolves limestone
Formation of Karst Landscapes
- Establishment of the water table in limestone
- Development of a cave network via dissolution (Dissolution maximized near the water table)
- Thick masses of recrystallized ice.
- Presently cover ~10% of Earth.
Forming a Glacier
- Cold local climate (polar latitudes or high elevation).
- Snow must be abundant; more snow must fall than melts.
- Snow must not be removed by avalanches or wind.
Flow from high to low elevation in mountain settings
- Vast ice sheets covering large land areas.
- Ice flows outward from thickest part of sheet.
- Two major ice sheets remain on Earth: Greenland, Antarctica
Basal Sliding / Movement of Glacier
- Significant quantities of meltwater forms at base of glacier.
- Water decreases friction, ice slides along substrate.
Plastic Deformation / Movement of Glacier
- Occurs below about 60 m depth.
- Grains of ice change shape slowly.
- New grains form while old grains disappear.
- Crevasses form at surface—upper zone too brittle to flow.
Zone of Accumulation
- Area of net snow addition.
- Colder temperatures prevent melting.
- Snow remains across the summer months.
Zone of Ablation
Area of net ice loss.
- The leading edge of a glacier.
- Ice always flows downhill, even during retreat.
Toe Position: Accumulation = Ablation
The glacial toe stays in the same place.
Toe Position: Accumulation > Ablation
The glacial toe advances.
Toe Position: Accumulation < Ablation
The glacial toe will retreat upslope.
- Bowl-shaped basins high on a mountain
- Form at the uppermost portion of a glacial valley.
- Freeze-thaw mass wasting chews into the cirque headwall.
- After ice melts, the cirque often becomes a tarn (lake).
- A “knife-edge” ridge.
- Formed by two cirques that have eroded toward oneanother
- A pointed mountain peak.
- Formed by three or morecirques that surround thepeak
- Glacial erosion creates a distinctive trough.
- Compare to V-shaped fluvial valleys.
- The intersection of a tributary glacier with a trunk glacier
- Trunk glacier incises deeper into bedrock.
- Troughs have different elevations.
- A waterfall results.
- U-shaped glacial troughs flooded by the sea.
- Accentuated by isostatic rebound.
Unsorted debris deposited by a glacier.
Forms along the flankof a valley glacier
Mid-ice moraine from merging of lateral moraines.
- Sediment dropped by glacial ice.
- Consists of all grain sizes—boulders to clay.
- Boulders dropped by glacial ice.
- These rocks are different from the underlying bedrock.
- Often, they have been carried long distances in ice.
- Sediments from an oceanic glacier
- Calving icebergs raft sediments away from the ice.
- Melting icebergs drop stones into bottom mud.
- Sediment transported by meltwater.
- Muds are removed.
- Sizes are graded and stratified.
- Grains are abraded and rounded.
- Wind-transported silt.
- Glaciers produce abundant amounts of fine sediment.
- Strong winds over ice blow the rock flour away.
- Deposits are unstratified and distinct in color.
- Long, aligned hills of molded lodgment till
- Asymmetric form—steep up-ice; tapered down-ice.
- Commonly occur as swarms aligned parallel to ice-flowdirection.
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