A2. Flooding & flood mitigation


Hydrographs show how a river handles extra water volume as a result of increased rainfall. It shows how quickly water falling within the river basin will reach the river channel. There are several elements to a hydrograph:

Storm hydrograph exercise

BBC Bitesize has some info on hydrographs.

BBC Rivers – hydrography looks at factors affecting the shape of hydrographs.

Hydrographs will be effected enormously by a whole range of different conditions. What kind of effect would these conditions have on a hydrograph?

small or large drainage basin?
impermeable rock (granite, clay) or permeable rock (limestone, sand)?
human activity – plantations or urbanisation?
vegetation – farmed fields or forest?
shape of the valley – steep sided or sloping gently?
prolonged, heavy rainfall or sudden showers?

This keynote on hydrographs will also be helpful.


The IB Geography syllabus requires you to be able to ‘discuss the natural and human causes and consequences of a specific river flood.’

The command word discuss requires you to ‘offer a considered and balanced review that includes a range of arguments, factors or hypotheses. Opinions or conclusions should be presented clearly and supported by appropriate evidence.’

Take a look at this great interactive animation of flooding and associated concepts:

We’re going to look at the 1998 Bangladesh floods, and use what we find to structure a case study of the flooding which took place in 2012.

These news articles from 2012-13 highlight the causes and effects of the flooding.


Presentation: Bangladesh flooding

Bangladesh in the front line of Climate Change?

Bocastle flood – BBC News looks at before and after (2014)

The Bocastle river flood from the RGS

New flood defence scheme at Bocastle

Bocastle: Then & now (floodblockbarrier.com)


Flood mitigation