Part 2 - Floods & Running Water

Hydrology

When does a flood HAPPEN?

When a river overflows onto a nearby land.

What does a flood LEAVE ON A FLOODPLAIN?

Silt

What are RIVER sediments?

Pieces of material carried by water (Sand, silt, clay, gravel)

What is an EROSIONAL AGENT?

Something that WEARS AWAY Earth’s surface.

What is the STRONGEST erosional agent in the notes?

Glaciers.

How do RAINDROPS cause erosion?

They loosen particles from the ground.

How does FLOWING STREAM WATER cause erosion?

Picks up + move particles

What is HYDRAULIC FORCE?

The force of moving water that can wear away rock.

How does sediment help erosion?

Sediment carried by water can help scrape/wear down rock.

What are the 3 types of SEDIMENT LOAD?

1. Dissolved

2. Suspended

3. Bed load

What is DISSOLVED LOAD?

Materials dissolved in water (salt) / NOT affected by velocity

What is SUSPENDED LOAD?

Small particles carried within water (Clay & Silt)

What is BED LOAD?

Material that moves along the bottom (Sand & gravel) / (Moves only at certain times)

What is SALTATION?

Sediment bouncing/skipping

What is CAPACITY?

(HOW MUCH SEDIMENT) - Max amount of sediment a stream can carry.

What INCREASED capacity?

DISCHARGE - (How much water flows past a point over time)

What is COMPETENCE?

(HOW BIG THE PARTICLES ARE) - A stream’s ability to transport particles based on size.

What INCREASES competence?

FLOW VELOCITY - (How fast water moves)

When does DEPOSITION happen?

When water slows down + sediment drops

What is CRITICAL SETTLING VELOCITY?

Water SLOWS down → sediment SINKS

What is SORTING?

Separating sediment by size.

What is ALLUVIUM?

Sediment deposited by a stream.

How does water speed AFFECT sediment?

Fast water = transports larger particles

Slow water = lets them settle

What 3 things can RIVER ENERGY cause?

Erosion, transportation, & deposition

What is BASE LEVEL?

Lowest point a stream can erode to

What is ULTIMATE BASE LEVEL?

Sea level

What is a LOCAL BASE LEVEL?

Temporary stopping point for erosion (lake)

RISING base level?

more DEPOSITION; sediment is dropped

LOWERING base level?

Erosion speeds up

What are BARS?

Temporary piles of sand/gravel in a stream

Where do DELTAS FORM?

Where a stream enters still water.

How does a DELTA GROW?

Grows outward / Slope (gradient) is gentler.

What are CHANNEL CHANGES?

Sediment build up, blocks river channel, splits/moves into STEEPER areas

What are DISTRIBUTARIES?

Carry water & sediment away from main channel

How do DELTAS evolve?

Small particles carried in water → Land sinks (Subsidence)

How do NATURAL LEVEES form?

Built by repeated floods along rivers

Where does COARSE vs. FINE sediment settle during floods?

COARSE: Near river

FINE: Spreads farther away