Week 10: Deltas and floods

How do deltas form?

When a stream enters standing water

Currents slow and loses competence, sediments drop out

Streams divide into a fan of small distributaries

Shape due to the interplay of flow, waves, and tides

When does flooding occur? What are seasonal and flash floods?

When discharge exceeds the channel capacity

Seasonal: Occurs slowly during spring snowmelt, summer monsoons, etc

Flash floods: Occur very quickly, often without warming

Floods are the most common and destructive geologic hazard

What is a recurrence interval?

The average number of years between floods of a particular size

How is flooding controlled?

Building away from high-risk areas

Allowing areas to flood to protect other areas

Building structures such as dams, levees, and seawalls