Geography Knowledge Map: Year 7: Rivers and Flooding
The Water Cycle
World Rivers
Waterfalls
Condensation
Clouds
4
2
5
1
3
7
6
4
Precipitation
Vegetation
Evaporation
Overland flow
Sea
Groundwater
Meanders
Boscastle Flooding
Bangladesh Flooding
How do meanders form?
What caused flooding at Boscastle?
Why does Bangladesh flood?
1. Water flows
faster on the outer
curve of the bend,
and slower on the
inner curve. So…
2. …the outer bank gets
eroded, but material is
deposited at the inner
bank. Over time…
5. The meander gets
tighter, with the edges
getting closer together.
Thanks to erosion and
deposition…
6. …the neck of
the meander
grows narrower
and narrower.
Eventually the
river just takes a
shortcut.
3. …as the
outer bank
wears away,
and the
inner one
grows, a
meander
forms.
4. As the process continues,
the meander grows more
‘loopy’.
7. Soon the
loop is sealed
off altogether.
It turns into
an oxbow
lake.
8. In time, the lake will get
covered with weeds, and fill
with soil, and disappear
1. Boscastle lies at the mouth of a small drainage basin.
2. The Paradise River and the River Valency meet in the
village.
3. Boscastle sits at the bottom of a very steep valley resulting
in a lot of surface runoff.
4. The valley floor is narrow and there is no floodplain.
5. Lots of rainfall in July and August meant the ground was
already waterlogged.
6. 130mm of rain fell between 12pm and 6pm, resulting in
nearly 1 million tonnes of water flowing through the
village.
7. High tie topped water from entering the sea.
8. A small landslide blocked the valley for a short time,
holding back water that eventually burst free.
9. A tarmac car park in the village caused very fast surface
runoff.
10. 2 warm air masses combined to produce intense rainfall.
1. It is a low and flat country – 75% of it is less than 10m
above sea level.
2. Most of Bangladesh is a delta , made up of silt deposited
from 3 rivers.
3. These rivers flow through Bangladesh from India and the
Himalayas, carying water and silt.
4. From May to September moist winds blow from the sea,
bringing monsoon rains.
5. Monsoon rains swell the river.
6. Larger numbers of trees have been cut down in India, Nepal
and Bangladesh.
7. The population of Bangladesh is rising fast, meaning more
people live on the land and on floodplains.
8. Floods bring 1 big benefit, the silt in the rivers keep the land
fertile so crops can grow.