Understanding Flooding and River Dynamics

What is a flood?

A flood is the overflow of water outside the normal course of a stream or river, usually due to excessive water flow.

How do rivers form?

Rivers form as water flows downhill, carving channels through erosion, which become deeper and capture more water.

What is a drainage network?

A drainage network is formed when small streams flow into larger streams, which flow into rivers and eventually the ocean.

What happens to water flow as a river curves?

Water moves at different speeds; it slows down on the inside of the bend and speeds up on the outside, causing erosion on the outside and deposition on the inside.

What is a floodplain?

A floodplain is a wide, flat valley floor created by sediment deposited on the inside of meanders of a meandering river.

What is discharge in the context of rivers?

Discharge is a measure of river flow, calculated as the product of the cross-sectional area and the flow speed (Q = Area x speed).

What factors influence flow speed in a river?

Flow speed is influenced by the slope of the river and the amount of water present; changes in area can also affect discharge.

What does equilibrium mean for a river?

Equilibrium means that the upstream discharge equals the downstream discharge, maintaining a balance in flow.

How do natural levees form?

Natural levees form during floods when sediment is deposited along the banks, gradually building them up.

What effect do levees have on river profiles?

Levees change the river profile to be steeper and deeper, which can protect nearby land but may also lead to land sinking over time.

What is runoff?

Runoff is the water that flows downhill after rain, calculated as Rainfall - Evaporation - Infiltration - Interception.

What is infiltration?

Infiltration is the process of water soaking into the ground, influenced by soil type and conditions.

What is interception in hydrology?

Interception is the temporary storage of water on surfaces like leaves or grass before it reaches the ground.

What causes flash floods?

Flash floods occur when there is little or no infiltration capacity, often in desert areas or when soil is frozen.

What is channelization?

Channelization is the alteration of a river's profile to make it steeper and more canyon-like, often through dredging or levee construction.

How do dams help with flood control?

Dams create lakes that act as storage areas for water, increasing interception and controlling downstream discharge.

What are retention ponds?

Retention ponds are structures that temporarily store water, slowing down runoff and reducing peak discharge.

What are floodways?

Floodways are undeveloped sections of floodplains that allow rivers to overflow during high flow, often used for parks or wildlife.

What are zoning laws in flood mitigation?

Zoning laws regulate the types of buildings allowed in flood-prone areas to reduce flood risk.

What is the economic impact of flooding in the US?

Flood damage costs the US over 8 billion dollars annually, with nearly 100 fatalities each year due to floods.

What role do insurance companies play in flood management?

Insurance companies charge extra for flood insurance and may charge more for properties in flood zones.

How can mortgage lenders influence flood risk?

Mortgage lenders can refuse to lend in flood-prone areas or require flood insurance for loans.

What is the relationship between infiltration capacity and flooding?

When soil is saturated with water, infiltration capacity decreases, increasing the likelihood of flooding.

How does vegetation affect infiltration?

Vegetation improves infiltration by breaking up soil and creating spaces for water to penetrate.

What happens to runoff speed compared to infiltrated water?

Runoff reaches rivers quickly, while infiltrated water contributes more slowly, affecting flood timing.

What is the significance of sediment supply during floods?

Floods can supply sediment to floodplains, which is essential for maintaining the ecosystem and land stability.