Water, Natural Hazards, and Ocean Systems

Comprehensive vocabulary flashcards covering fluvial geomorphology, stream profiles, flood mechanisms, hydrological calculations, atmospheric circulation cells, and oceanic currents.

Meandering Stream

A river channel pattern characterized by a single channel with a sinuous, curving course; it represents the most common channel pattern found across floodplains.

Braided Stream

An uncommon stream pattern formed by an interlacing network of converging and diverging channels, typically occurring in environments with high sediment loads and high flow velocity.

Point Bar

A low-gradient depositional ridge formed along the inner curve of a river bend where flow velocity drops.

Cut Bank

A steep, eroded riverbank located along the outer curve of a meandering stream where velocity and erosive energy are highest.

Thalweg

The line following the deepest continuous part and zone of highest velocity within a river channel.

Meander Cutoff

A new, shorter channel created when a river breaches the narrow neck of an exaggerated meander loop, bypassing the bend.

Oxbow Lake

A curved, crescent-shaped body of standing water created when a meander cutoff abandons and isolates a loop from the active river channel.

Local Base Level

The temporary lower limit of stream downcutting governed by an intermediate feature such as a lake, resistant rock layer, or reservoir along the stream's profile.

Ultimate Base Level

The lowest theoretical elevation to which any subaerial stream network can erode, defined globally by sea level.

Lockport Dolostone

The hard, erosion-resistant rock layer that caps the Niagara escarpment, maintaining Lake Erie at a higher elevation than Lake Ontario and producing Niagara Falls.

Natural Levee

An elevated ridge of coarse sediment bordering a stream channel, deposited during overbank flow when floodwaters immediately lose velocity after breaching the channel banks.

Stream Discharge

The volume of water passing through a stream cross section per unit time, calculated by multiplying cross-sectional area ($\text{width} \times \text{depth}$) by flow velocity ($\text{distance}/\text{time}$).

Recurrence Interval ($RI$)

The average number of years between flood events of a specified or greater magnitude (for example, a 100-year flood occurs on average once every $100\,\text{years}$).

Artificial Levee

An engineered earthen ridge or barrier built along river banks to contain floodwaters within the channel and protect settlements and infrastructure on the floodplain.

Lag Time (Hydrology)

The duration between peak precipitation and peak river discharge, which decreases significantly in urbanized watersheds due to an increase in impermeable surfaces.

Glacial Lake Missoula

An ancient ice-dammed lake that repeatedly failed catastrophic ice-dam breaches during the Ice Age, discharging megafloods that sculpted the Channeled Scablands.

Coriolis Effect

The apparent deflection of moving air and water caused by Earth's planetary rotation, causing objects to veer to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Trade Winds

Steady, persistent low-latitude surface winds blowing toward the equatorial trough from the subtropical high-pressure belts ($30^\circ$ latitude), known as the northeast trade winds in the Northern Hemisphere and southeast trade winds in the Southern Hemisphere.

Thermohaline Circulation

The global oceanic conveyor system driven by density contrasts originating from variations in temperature and salinity, moving warm shallow currents poleward and returning cold, salty water as deep currents.