M odu le 8 – ( L3 1 – L3 4 ) : “St or m
l
d
”
W a t e r & Flood M a n a ge m e n t
”:
St or m w a t e r m a n a ge m e n t , de sign of dr a in a ge syst e m , flood r ou t in g t h r ou gh ch a n n e ls a n d r e se r voir flood con t r ol a n d r ou t in g t h r ou gh ch a n n e ls a n d r e se r voir , flood con t r ol a n d r e se r voir ope r a t ion , ca se st u die s.
3 4
Flood Con t r ol &
M a n a ge m e n t
L34
Floods, Causes, Flood dam ages, Flood
Floods, Causes, Flood dam ages, Flood
forecast ing & warning, Flood cont rol,
forecast ing & warning, Flood cont rol,
Reservoir operat ion Flood
Reservoir operat ion Flood
Reservoir operat ion, Flood
Reservoir operat ion, Flood
Managem ent
Managem ent
Keywords:
Keywords:
Flooding, flood cont rol, flood Flooding, flood cont rol, flood Managem ent .Flooding Problem s
Flooding Problem s
Floods affect lives of m ore t han 65 m illion people per year
More t han any ot her t ype of disast er, including w ar, drought and
Em ergency cost s; Physical dam age
– St ruct ures, ut ilit ies, aut os, crops, et c.
Lost value of public agency services
Causes of Floods
Causes of Floods
A Flood
can occur when a river exceeds it s bank full st age and wat er will subsequent ly inundat e t he adj acentdi
surrounding area.
H e a vy r a in fa ll - long periods of heavy rainfall will lead
t o an increase in surface runoff and increase in river level.
Sn ow m e lt - wat er in st orage is oft en freed by Spring
m elt s increasing surface runoff m elt s increasing surface runoff.
D e for e st a t ion - cut t ing down of t rees leads t o a
Causes of Floods
Causes of Floods
Ur ba n iz a t ion
-
t arm ac and concret e surfaces are
im perm eable and lead t o an increase in surface
ff
favourable condit ions for int ense flooding.
For exam ple,
in a cit y
t hat is t ot ally served by
st orm drains and w here 60% of t he land surface is
covered by roads and buildings floods are alm ost
covered by roads and buildings, floods are alm ost
Causes of Floods
Causes of Floods
Heavy
rainfall?
Snow
melt?
Rivers are m ore liable t o flood? –
besides t hese?
besides t hese?
Urbanisation
De-forestation
Result s of Flooding
Result s of Flooding
Flooding great ly increases t he river’s energy so it can do
m ore work. The deeper and fast er flowing river can carry m ore loado e oad
Most rivers t urn brown because of t he large am ount of
sedim ent carried in suspension.
The am ount of erosion carried out by hydraulic act ion The am ount of erosion carried out by hydraulic act ion
and abrasion is great ly increased.
Flood Dam ages
Flood Dam ages
Sh or t t e r m
Sh or t t e r m
Loss of life
Dest ruct ion of propert y
Dest ruct ion of propert y
Flood For e ca st in g
Flood for e ca st in g - use of real- t im e precipit at ion
and st ream flow dat a in rainfall- runoff & st ream flow
and st ream flow dat a in rainfall runoff & st ream flow rout ing m odels t o forecast flow rat es and wat er levels for periods ranging from a few hours t o days ahead, depending on t he size of t he wat ershed or river basin
depending on t he size of t he wat ershed or river basin.
Flood forecast ing can also m ake use of forecast s of
precipit at ion t o ext end t he lead- t im e available.
Forecast ing syst em m ay account for: snowm elt ;
flood plains and washlands; flood plains and washlands;
Flood For e ca st in g & W a r n in g
Flood forecast ing t hrough range of hydrodynam ic/
snowm elt / flood rout ing m odels. channel flows or river levels at various locat ions,
“Flood w arning" is t he t ask of m aking use of t hese
Flood Con t r ol M e a su r e s
Flood cont rol m easures – St ruct ural & nonst ruct ural St ruct ural m easures:
St ruct ural m easures:
– Levees: em bankm ent const ruct ed parallel t o t he course of st ream t o prevent inundat ion of large
d l l
areas – Design considerat ion: locat ion, slope
st abilit y, seepage, int erior drainage, t op widt h & free board, erosion & scour prot ect ion
– Groins: dikes ext ending from t he bank of river – prot ect bank against erosion
Cut offs art ificial excavat ed cut offs t o st raight en – Cut offs –art ificial excavat ed cut offs t o st raight en
channel
Flood Con t r ol M e a su r e s
St ruct ural m easures:
– Channelizat ion –clearance st raight ening widening – Channelizat ion –clearance, st raight ening, w idening,
deepening & lining
– Bridge m odificat ion – rem oval, replacem ent , widening, raising
– Flood proofing – floodplain or flood hazard zones – by ring levees or flood wall
by ring levees or flood wall
– Det ent ion basins – sm all im poundm ent s designed t o t em porarily st ore st orm runoff & release
Flood Con t r ol M e a su r e s
Non- St ruct ural m easures:
Est ablishm ent of regulat ory floodplains
Est ablishm ent of regulat ory floodplains
St orm wat er regulat ions
Flood zones
Flood zones
Wat ershed m anagem ent plans
Flood em ergency planning
Flood em ergency planning
Relocat ion of flood prone unit s
Flood Cont rol Managem ent
Flood Cont rol Managem ent
There are a num ber of ways m anaging floods:
1. Affor e st a t ion - plant ing t rees increases int ercept ion
t d d f ff
rat es and reduces surface runoff.
2. D a m s a n d Re se r voir s - t hese hold back and regulat e
t he flow of river wat er. Can be used as fresh wat er supply pp y and generat ion of HEP.
3. D ive r sion Ch a n n e ls a n d ba sin - overflow channels
which t ake surplus wat er out of a river in t im es of flood which t ake surplus wat er out of a river in t im es of flood.
4. Ch a n n e l St r a it e n in g a n d D r e dgin g - sm oot hens t he
Flood Cont rol Managem ent
Flood Cont rol Managem ent
5 . Ar t ificia l Le ve e s - m akes river banks higher
t herefore holding m ore wat er.
6. Cu lve r t s - sem i circular, sm oot h channels increase
velocit y and get s wat er away from urban areas as quickly as possible.
7 Re ve t m e n t s Ch a n n e l W a lls ga bion s
7. Re ve t m e n t s, Ch a n n e l W a lls, ga bion s
-st rengt hen river banks from erosion using large lum ps of st one – see over
8 Re st r ict e d u se of flood- pla in s - legislat ion 8 . Re st r ict e d u se of flood- pla in s legislat ion,
higher select ive insurance prem ium s/ refusal t o insure part icular locat ions.
9 .Co- or din a t e d flood w a r n in g9 .Co or din a t e d flood w a r n in g and em ergence and em ergence
Flood Con t r ol & Re se r voir Ope r a t ion
Dam s & Reservoirs have helped im m ensely in
at t aining self sufficiency in food grain product ion at t aining self sufficiency in food grain product ion besides flood cont rol and drought m it igat ion.
Flow dept h in rivers – depends on reservoir releases
d f h f
A reservoir is a deposit ory for t he st orage of wat er, up
t o a m axim um level.
Since Since spilling wat er im pliesspilling wat er im plies passage t hrough a crit ical passage t hrough a crit ical
hydraulic sect ion, a dynam ic st orage volum e can be filled up only during spills.
Operat ional pool volum e bet ween t he m inim um level
Operat ional pool - volum e bet ween t he m inim um level
Flood Con t r ol & Re se r voir Ope r a t ion
Operat ional pool is concept ually divided int o
conservat ion and flood cont rol pools.
Maxim um possible em pt y space is desirable for flood Maxim um possible em pt y space is desirable for flood
cont rol, while wat er st orage is required for t he rem aining obj ect ives of wat er supply, irrigat ion, hydropower et c
hydropower, et c.
Since flood risk differs according t o t he season, t he
flood cont rol pool t ypically varies according t o t he t im e of t he year.
Single reservoir – cont rolled operat ion
Flood cont rol t hrough syst em of reservoirs A cascade
Flood cont rol t hrough syst em of reservoirs - A cascade
Flood Re se r voir M a n a ge m e n t
Flood cont rol m anagem ent approach - consider t he
flood pool as a rest rict ion for t he opt im izat ion or sim ulat ion of t he conservat ion pool.
sim ulat ion of t he conservat ion pool.
Operat ion under flood condit ions can be perform ed
t hrough a previously set rule curve or wit hin a real
operat ional forecast ing and warning availabilit y operat ional forecast ing and warning availabilit y.
Flood Cont rol vs. Flood Risk Managem ent
Floods have occurred t hroughout t im e, and are not
necessarily dam aging necessarily dam aging
Early legislat ion aut horized “flood con t r ol” in
response t o devast at ing losses
’ ll l fl d b d f
We can’t really con t r ol floods, but w e can m odify
wat er flows in space and t im e
Corps’ m ission is t o assist wit h and provide leadership Corps m ission is t o assist wit h and provide leadership
in m anaging flood risk; t his includes m aking Govt . invest m ent s for r e du cin g da m a ge s from floods “A complete description of a plan includes all structural
ll
A complete description of a plan includes all structural,
nonstructural, legal, and institutional features, both proposed & existing, that contribute to intended flood control outputs.”
Flood Risk Managem ent
St t i G l St rat egic Goals
1 Provide current accurat e floodplain inform at ion t o t he 1. Provide current accurat e floodplain inform at ion t o t he
public and decision m akers.
2. I dent ify and assess flood hazards posed by aging flood
dam age reduct ion infrast ruct ure.
3. I m prove public awareness and com prehension of flood
risk risk.
4. I nt egrat e flood dam age and flood hazard reduct ion
program s across local, st at e, and Federal agencies.
5. I m prove capabilit ies t o collaborat ively deliver and
sust ain flood dam age reduct ion and flood hazard m it igat ion services t o t he nat ion.
Flood Pr oble m - Un ce r t a in t y
I n flood dam age- reduct ion planning, uncert aint ies include
– Fut ure hydrologic event s: st ream flow and rainfall
choice of dist ribut ion and values of param et ers
– Sim plified m odels of com plex hydraulic phenom ena
t i d t i li t f t t t i l
geom et ric dat a, m isalignm ent of st ruct ure, m at erial
variabilit y, and slope and roughness fact ors – Relat ionship bet ween dept h & inundat ion dam agep p g
st ruct ure values and locat ions, how t he public will
respond t o a flood
St t l d t h i l f h – St ruct ural and geot echnical perform ance w hen
Flood Pr oble m & Re st or a t ion
Pla n n in g- Before event t hreat ens D e t e ct ion - ongoing inform at
ion-gat hering syst em - provide warning
g g y p g
t o m onit or prevent ion & m it igat ion syst em s.
Pr e pa r a t ion -Pr e pa r a t ion Com m unicat ion, Com m unicat ion, ht t p: / / w w w.nfrm p.us
needed resources, evacuat ion et c
Fir st r e spon se - Once t he event
has occurred, t he negat ive has occurred, t he negat ive
consequences can be m inim ized -appropriat e act ion t o save lives; provide food, shelt er, & clot hing t o provide food, shelt er, & clot hing t o survivors.
Re con st r u ct ion - rebuilding
Floods in I n dia
Floods occur in alm ost all rivers basins of I ndia.
Heavy rainfall inadequat e capacit y of rivers t o
Heavy rainfall, inadequat e capacit y of rivers t o
carry t he high flood discharge, inadequat e
drainage t o carry away t he rainw at er quickly t o
g
y
y
q
y
St ream s/ Rivers are t he m ain causes of floods.
I ce j am s or land slides blocking st ream s;
t
h
d
l
l
fl
d
t yphoons and cyclones also cause floods.
Excessive rainfall com bined w it h inadequat e
Floods in I n dia
MOWR has assessed t he area liable t o floods as 35
Flood H a z a r d M a p of I n dia
• Floods being a nat ural
phenom ena, t ot al elim inat ion or cont rol - not possible nor econom ically viable.y
• Flood m anagem ent aim s at providing reasonable
prot ect ion against dam age at prot ect ion against dam age at reasonable econom ic cost s.
ht t / / i i
Flood H a z a r ds in I n dia
been adopt ed in different st at es. St ruct ural m easures- st orage reservoirs, flood St ruct ural m easures st orage reservoirs, flood
em bankm ent s, drainage channels, ant i- erosion w orks, channel im provem ent works, det ent ion basins et c.
l fl d f fl d l
Non- st ruct ural m easures - flood forecast ing, flood plain
Flood H a z a r ds in I n dia
Various flood m anagem ent m easures undert aken: 1. Flood em bankm ent s 34397.61 km
2. Drainage channels 51317.50 km 3. Towns prot ect ion works 2400 Nos. 4 Villages raised 4721 Nos
4. Villages raised 4721 Nos.
Reservoirs const ruct ed wit h exclusive flood cont rol
st orage - Mait hon, Panchet , Tilaiya & Konar in Dam odar Valley; Chandil dam on Subarnarekha river, Rengali dam on Brahm ani river et c.
A live st orage of 177 billion cubic m et er creat ed so far in A live st orage of 177 billion cubic m et er creat ed so far in
t he various reservoirs for irrigat ion, hydropower
Flood H a z a r ds in I n dia
The flood m anagem ent m easures undert aken so far
Flood Forecast ing Net w ork in I ndia
Flood forecast ing has been recognized as one of t he
m ost im port ant , reliable and cost - effect ive non-m ost inon-m port ant , reliable and cost effect ive non st ruct ural m easures for flood m anagem ent .
Recognizing t he crucial role it can play, Cent ral Wat er
C i i Mi i f W R h
Com m ission, Minist ry of Wat er Resources has set up a net work of forecast ing st at ions covering all im port ant flood prone int erst at e rivers. p
Exam ple: AP cyclone hazard
m it igat ion proj ect out com es
Hazard m it igat ion st udies ( int ernat ional consult ant s)
Hazard m it igat ion st udies ( int ernat ional consult ant s)
I MD early w arning capacit y t hrough Doppler radar
I nfrast ruct ure creat ion and rest orat ion
– Floods – drains & em bankm ent s
– Road rest orat ion
St orm shelt ers
– St orm shelt ers
– Elect ricit y t ransm ission and dist ribut ion
Concluding Rem arks
Recognit ion of linkage bet ween nat ural hazards and
developm ent developm ent
Connect ing developm ent al program s t o disast er
m anagem ent
d ( h l )
Forecast ing and warning ( t echnology use) Cont ingency planning
– Food grains availabilit yFood grains availabilit y – Preparedness
Adapt ive capacit y by creat ing a m anagem ent syst em However, focus st ill on relief; recovery and adapt ive
Re fe r e n ce s
Subrahm anya, K( 2007) . Engineering Hydrology, Tat a McGraw- Hill,
New Delhi, 294- 300
A. Prakash ( 2004) – Wat er Resources Engineering, ASCE press, ( ) g g, p ,
Rest on, USA
Chow , V.T., Maidm ent , D.R., and Mays, L.W. ( 1988) . Applied
Hydrology, McGraw- Hill,y gy, ,I nc., New York,
Bedient , P.B.,Huber, C.W. ( 1988) . Hydrology and Flood Plain
Analysis, Addison- Wesley Publishing Com pany ht t p: / / wrm in nic in
Tu t or ia ls - Qu e st ion !.?.
Crit ically St udy t he flooding problem s in
I ndia ( w ww wrm in nic in)
I ndia ( www .w rm in.nic.in)
What are t he m easures t aken by Govt . t o
What are t he m easures t aken by Govt . t o
y
y
reduce flood im pact s?.
reduce flood im pact s?.
How w e can have bet t er flood cont rol
How w e can have bet t er flood cont rol
Se lf Eva lu a t ion - Qu e st ion s!.
Describe flood and relat ed problem s.
I llust rat e short t erm and long t erm flood
dam ages.
Discuss various flood cont rol m easures.
Different iat e bet w een st ruct ural &
non-st ruct ural m easures.
I llust rat e flood cont rol and reservoir
I llust rat e flood cont rol and reservoir
Assign m e n t - Qu e st ion s?.
g
Q
What are t he im port ant causes of
floods?
floods?.
Discuss flood forecast ing and
w arning.
What are t he im port ant w ays of flood
p
y
cont rol m anagem ent ?.
Discuss t he flood risk m anagem ent &
Discuss t he flood risk m anagem ent &
Dr. T. I. Eldho Dr. T. I. Eldho
Professor, Professor,
Department of Civil Engineering, Department of Civil Engineering, pp gg gg
Indian Institute of Technology Bombay, Indian Institute of Technology Bombay, Mumbai, India, 400 076.
Mumbai, India, 400 076. Email:
Email: [email protected]@iitb.ac.in Email:
