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Page 2

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­ RIVERS,
FLOODS
AND MANAGEMENT
DRAINAGE BASINS:
It
i
s an
area sur
rounding
the
river
where
the
rai
n f
all
ing
on t
he l
and f
lows i
nto
that
r
iver
(
catchment
).
The boundary
o f
a
drai
n age
basin
is
the
w at
ershed
­ any
preci
pit
ati
on t
hat
fal
ls
beyond t
he
w at
er
shed ent
e r
s a
dif
ferent
basi
n.…read more

Page 3

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WATER BALANCE BUDGET:
Wa ter
balance
is
w or
ked
out
from i
npu t
s and
out
puts i
t
a f
fect
s how much
w at
er
is
stored
in
the
basi
n.
1. I n
w et
seasons,
precipi
tat
ion
e xceeds
evapot
ranspir
ati
on. Thi
s cr
ea t
es a
w at
e r
sur
plus.…read more

Page 4

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If
ground i
s al
ready water
logged then i
nfi
lt
rat
ion
is
reduced
and surf
ace runoff
i
ncreases.
S ur
face
runoff
i
s muc h
fast
er t
han
thr
o ughf
low
or basef
low so
rai
n water
reaches t
he ri
ver
mo re
quickl
y,
reducing
ti
me l
ag.…read more

Page 5

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TRACTI
O N ­
ver
y l
arge
par
ti
cl
es
­ boul
der
s ­
are
pushed
along
the
ri
ver
bed
by
the
for
ce
of
the
w at
er.
DEPOSITION:
Occurs when the river loses energy
and as
a resul
t,
l
oad i
s deposi
ted.
· R educed r
a inf
all =
lowe r
di
scharge
= ri
ver
slows down and
has l
ess ener
gy.…read more

Page 6

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I
n t
he upper
course
of
a ri
ver:
st
eep gradi
ent,
r
iver
hi
gh
a bove
sea l
evel
= l
ots
of
gravi
tat
ional
pot
ent
ial
ener
gy.
I
n t
he middl
e cour
se of
a r
iver:
gr
adient
decr
eases =gr
avit
ati
onal
potent
ial
energy
convert
ed t
o ki
net
ic
ener
gy =
veloci
ty
incr
eases.…read more

Page 7

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Channel roughness = greatest in upper stages of river. Although gr
ad i
ent
is
s t
e ep, ri
ve r
l
oses a
lot
of
energy
to f
ric
tion
=
d ischa r
g e
and vel
oci
t
y
are
lowest
duri
n g
n orma l
co ndit
ions.
6)
Lower stages = river banks and bed is smooth = less friction = less energy is lost = discharge and
velocity highest at this stage.…read more

Page 8

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The combination of erosion and deposition exaggerates the bends unt
il
l
arge me anders are
forme d.
The comb ined
pro cesses
also
c reate an
asymmetric crosssection.
8 )
Oxbow lakes are formed when the neck of the loop of a meander is broken through, often
during flooding. Deposition dams off the loop
leaving an oxbow lake.…read more

Page 9

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I
f
the
ri
ver'
s vel
oci
ty
drops,
or
the
sedi
men t
l
oad becomes t
oo much
for
t
he r
iver
t
o car
ry,
sedi
ment
us
deposi
ted
in
the
channel
.
3)
Thi
s causes
the
ri
ver
to
divi
de i
nto
smal
l,
wi
n di
ng channel
s t
hat
event
ual
ly
rej
oin
to
for
m a si
ngl
e channel
.…read more

Page 10

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FOR MA TI
O N
1)
Wh en a
ri
ver
reaches t
he sea,
t
he energy
of
the
river
i
s absor
bed by
the
slower
movi
n g
w at
er
of
the
sea.
2)
This
causes t
he ri
ver
to
deposit
i
ts
load.…read more

Comments

aun

ur a star this is absuloutly fab. lol sorry for the spelling i would give this 10 out 5

Thomas Ives

brilliant.... thank you for putting this on, it's very helpful

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