Surface Hydrology and River Flow Study Guide

Fluvial Geomorphology

The study of how rivers and streams shape the landscape through erosion, transportation, and deposition.

Surface Hydrology

Focuses on the movement, distribution, and properties of water on Earth's surface.

Hillslope Processes

Involve the movement of water and sediment on slopes.

Channel Processes

Pertains to water flow within river channels.

Hydrologic cycle consists of

Condensation, evaporation, precipitation, and transpiration

Hydrologic Cycle

Key processes include condensation, evaporation, precipitation, and transpiration.

Condensation

Water vapor cools and turns into liquid droplets.

Evaporation

Water changes from liquid to gas due to solar energy.

Precipitation

Water falls from clouds as rain, snow, sleet, or hail.

Transpiration

Water released from plants into the atmosphere.

Hydrologic cycle in relation to surface water hydrology

The hydrologic cycle governs water availability, runoff, and infiltration, which are critical for surface hydrology

Surface Water Routing

The processes by which water moves through the landscape.

Infiltration

Water enters the soil and replenishes groundwater.

Factors influencing pathways

Soil permeability, land cover, slope gradient, and rainfall intensity determine infiltration vs. runoff.

Runoff

Water flows overland when infiltration capacity is exceeded.

Impervious Surfaces

Pavement and buildings that reduce infiltration, increasing urban runoff and flood risks.

Drainage Basin

The land area that channels precipitation to a river system.

Overland Flow

Water moving across the land surface before entering channels.

Rills & Gullies

Small, linear erosion features that can evolve into larger channels.

River Channel

A natural conduit for water flow.

Discharge (Q)

The volume of water flowing through a river section per unit time, calculated as Q = A * V (area × velocity).

Stage

Water level height relative to a reference point.

2 Methods to measure flow

Float method and velocity-area method

Float Method

Measures surface velocity using floating objects.

Velocity-Area Method

Uses current meters to determine average velocity.

Bankfull Discharge

Maximum capacity before overflow.

Flood Frequency

Statistical probability of flood events.

Floodplains

Areas adjacent to rivers that flood periodically.

Geomorphic processes

Erosion, transpiration, and deposition

Erosion

Removal of surface material.

Transportation

Movement of sediments by water.

Deposition (geomorphic process)

Sediments settle when water loses energy.

3 Erosion components

Detachment, transport, and deposition

Detachment

Soil particles are loosened by water impact.

Transport

Particles move via overland flow.

Deposition (hillslope process)

Materials settle in lower-energy environments.

Factors depending erosion

Rainfall intensity, slope steepness, soil type, vegetation cover, and land use practices.

3 Erosion mechanisms

Hydraulic acid, abrasion, and solution/corrosion

Hydraulic Action

Water pressure erodes channel banks.

Abrasion

Sediments scrape against channel surfaces.

Solution/Corrosion

Dissolution of minerals in water.

Bed Load

Particles move along the riverbed.

Suspended Load

Fine sediments carried in water column.

Dissolved Load

Minerals dissolved in water.

Deposition Conditions

Occurs when water velocity decreases.

Hjulstrom's Curve

Demonstrates erosion, transport, and deposition thresholds based on particle size and velocity.

3 Stream channel patterns

Meandering, braided, and straight

Meandering

Winding, sinuous channels with point bars and cut banks.

Braided

Multiple channels interwoven due to high sediment load.

Straight

Relatively linear channels.

Cut Banks & Point Bars

Erosion on outer bends, deposition on inner bends.

Floodplains (feature)

Flat areas prone to periodic flooding.

Terraces

Former floodplain levels indicating past river activity.

Oxbow Lakes

Isolated meander loops formed by cutoff.

Mississippi River and human impact

Engineering projects have altered natural sediment deposition and channel migration.

Excess Energy Usage

Erosion, lateral migration, and vertical incision.

Knickpoint Erosion

Waterfalls retreating upstream due to differential erosion (e.g., Niagara Falls).

Capillary vs. Groundwater

Capillary water is held in soil pores, whereas groundwater exists in saturated zones.

Water Table & Seasonal Variation

Affects stream baseflow and wetland levels.

Perched Water Table

An isolated, elevated groundwater layer.

Discharge Areas

Springs, streams, and wetlands rely on groundwater contributions.

Aquifer

A body of rock or sediment that stores groundwater and allows the flow of groundwater.

Aquiclude

A body of rock that will absorb water slowly, but will not transmit it fast enough to supply a well.

Confining layer

A place in the aquifer where impermeable rock covers permeable rock

Recharge areas

Areas where water percolates through the ground into groundwater

Chemical Weathering

Carbonation dissolves limestone.

Key Ingredients of Karst Topography

Soluble rock, water, carbon dioxide.

Landforms in Karst Topography

Sinkholes, caves, stalactites, stalagmites, columns.

Rivers vs. wetlands

Wetlands were often drained for agriculture but are now recognized for ecological value.

Channelization, levees, and wetland drainage

Used for flood control and agriculture but have ecological consequences.

Dams

Built for flood control, hydroelectricity, irrigation; impact sediment transport and ecosystems.

Modern conservation

Clean Water Act, dam removal initiatives

Clean water act

(CWA, 1972) set maximum permissible amounts of water pollutants that can be discharged into waterways; aims to make surface waters swimmable and fishable

Hydrograph Interpretation

Baseflow, storm flow, peak discharge.

Urbanization impact

Increased runoff due to impervious surfaces

Green Infrastructure

Sustainable solutions like rain gardens and permeable pavements.

Overuse Consequences of groundwater

Lower water tables, land subsidence.

Drawdown

A lowering of the groundwater level caused by pumping.

Cones of depression

Result when the rate of water removed from a well is greater than the rate flowing into the well from the aquifer

Salt water intrusion

Near the coast, over-pumping of groundwater causes saltwater to move into the aquifer

Wave Properties

Crest, trough, wavelength, height.

Wind Factors

Speed, duration, and fetch influence wave size.

Tides

Driven by gravitational forces, affecting coastal erosion.

Erosional Landforms

Sea cliffs, arches, stacks.

Transportation and deposition

Longshore drift, beaches, barrier islands

Human impact of coastal erosion and deposition

Jetties, seawalls, and beach nourishment.