Drainage basins and flooding, Geo Final Exam!

What are drainage divides?

The boundaries between drainage basins

What are we in (Columbia)?

We are in the Santee watershed

What do drainage basins have over geological time?

Drainage basins have reversed flow over geologic time. (example, Amazon watershed)

How do we calculate stream discharge?

channel width X water depth X stream velocity

What is a flood recurrence interval?

the average time that will pass between
floods of a given discharge.

How is a “500-year flood” determined?

1 and 500 chance.

What are the effects of urban development on stream discharge and time intervals between rainfall and discharge?

Urban development makes streams respond faster and more intensely to rainfall, increasing flood risk and reducing groundwater recharge.

What is the Case study: October 2015 flooding in Columbia?

It was a 500-year flood and driven by
clockwise rotation around high-pressure system over mid-Atlantic and counterclockwise rotation around a low-pressure system over Florida.