L34– Flood Control Management
M odu le 8 – ( L3 1 – L3 4 ) : “St or m W a t e r & Flood M a n a ge m e n t l d
”: ”
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. Flood Con t r ol & 3 4 3 4 M a n a ge m e n t M a n a ge m e n tFlood Con t r ol & M a n a ge m e n t Flood Con t r ol & M a n a ge m e n t
L34 L34 L34– L34
Topics Cove r e d Topics Cove r e d
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
Flooding, flood cont rol, flood Flooding, flood cont rol, flood Keywords: Keywords:
Managem ent . Managem ent . a age a age e t e t 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 fam ine
I n East & Sout heast Asia, during t he m onsoon season, rivers swell t o over 10 t im es t he dry season flow
About 13% ( of 45 000) of all large dam s in t he w orld – in m ore
About 13% ( of 45,000) of all large dam s in t he w orld in m ore
t han 75 count ries – have a flood m anagem ent funct ion Flood Dam age: I j i d l f lif S i l di t i I l
I nj uries and loss of life; Social disrupt ion; I ncom e loss
Em ergency cost s; Physical dam age – St ruct ures, ut ilit ies, aut os, crops, et c.
Lost value of public agency services – Police & fire prot ect ion, hospit als, et c.
Tax loss: Propert y and sales
Tax loss: Propert y and sales
Causes of Floods Causes of Floods
can occur when a river exceeds it s bank full
A Flood
st age and wat er will subsequent ly inundat e t he adj acent surrounding area. di
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
reduct ion in int ercept ion rat es and an increase in surface runoff. This m ay also lead t o rapid erosion rat es due t o a lack of st abilit y in t he soil subsurface. 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 runoff. ff
Aft er urbanizat ion t he lag t im e is short ened, peak flow is great ly increased, and t ot al run off is flow is great ly increased and t ot al run- off is com pressed int o a short er t im e int erval – 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 six t im es m ore num erous t han before urbanizat ion
Causes of Floods Causes of Floods Heavy
Snow rainfall? melt?
Rivers are m ore liable t o flood? – besides t hese? besides t hese? De-forestation U ba sat o Urbanisation 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 load o 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.
How does t his happen?
I t h l I n t he low lands m any feat ures are form ed during l d f t f d d i flooding:
- – Levees – Flood plain deposit ion
- – Ox- bow lakes
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
Crop dam age
Loss of com m unicat ion
Fresh w at er pollut ion
Loss of pow er
Lon g t e r m Lon g t e r m
Replacing w hat is lost or dam aged
Governm ent s have t he funds t o rebuild t he
Governm ent s have t he funds t o rebuild t he infrast ruct ure- e.g. roads, w at er t reat m ent et c
Crop dest ruct ion can lead t o fam ine
Flood For e ca st in g
Flood for e ca st in g - use of real- t im e precipit at ion
and and st ream flow st ream flow dat a in dat a in rainfall runoff rainfall- runoff & & st ream flow 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 depending on t he size of t he wat ershed or river basin 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 defenses, including cont rol- gat es et c.;
t idal effect s near t he sea, and sea- surges.
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. snowm elt / flood rout ing m odels.
Flood forecast ing is an im port ant com ponent of flood w arning ,
Dist inct ion bet w een t he t wo is t hat t he out com e of b h h h f
flood forecast ing is a set of forecast t im e- profiles of channel flows or river levels at various locat ions,
“ Flood w arning " is t he t ask of m aking use of t hese forecast s t o m ake decisions about whet her warnings of floods should be issued t o t he general public or of floods should be issued t o t he general public or whet her previous warnings should be rescinded or ret ract ed.
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 areas – Design considerat ion: locat ion, slope d l l 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 Bypass – divert a port ion of flood flow
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 gradually.
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 insurance – based on flood risk zones
Flood forecast ing & w arning. 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
rat es and reduces surface runoff. t d d f ff
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
channel t o increase t he speed ( velocit y) of t he river and get wat er out of t he drainage basin as quickly as possible.
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 8 . Re st r ict e d u se of flood- pla in s - legislat ion 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 g 9 .Co- or din a t e d flood w a r n in g and em ergence and em ergence
react ion procedures e.g. Environm ent Agency Flood wat ch
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
A reservoir is a deposit ory d for t he st orage of wat er, up f h f t o a m axim um level.
Since Since spilling wat er im plies spilling 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 Operat ional pool - volum e bet ween t he m inim um level volum e bet ween t he m inim um level
at which cont rolled releases can be m ade & m axim um st at ic full pool.
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 Maxim um possible em pt y space is desirable for is desirable for flood 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 Flood cont rol t hrough syst em of reservoirs - A cascade A cascade
of Reservoirs is m ore effect ive in t erm s of peak delay t han t he equivalent st orage capacit y com bined in one reservoir i
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
t im e fram ew ork. t im e fram ew ork
The second approach uses as m uch real t im e
inform at ion as possible from t he whole syst em , as well as it s near fut ure.
Decision syst em is closely relat ed t o t he real t im e
operat ional forecast ing and warning availabilit y. operat ional forecast ing and warning availabilit y
Real t im e flood m anagem ent
Sedim ent relat ed problem 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
We can’t really con t r ol floods, but w e can m odify ’ ll l fl d b d f 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 . e e ll invest m ent s for r e du cin g da m a ge s from floods
h h a a n n n n “A complete description of a plan includes all structural A complete description of a plan includes all structural, a a in in c c nonstructural, legal, and institutional features, both proposed o o ir ir i i n n m m & existing, that contribute to intended flood control outputs.” Flood Risk Managem ent
St rat egic Goals St t i G l 1.
1 Provide current accurat e floodplain inform at ion t o t he 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. m it igat ion services t o t he nat ion. Risk Reduct ion Act ions
Ref: US Arm y Corpse of Engineers: ht t p: / / www.nfrm p.us/ present at ions.cfm
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
geom et ric dat a, m isalignm ent of st ruct ure, m at erial t i d t i li t f t t t i l variabilit y, and slope and roughness fact ors
- – Relat ionship bet ween dept h & inundat ion dam age p p
g
st ruct ure values and locat ions, how t he public will respond t o a flood
- – St ruct ural and geot echnical perform ance w hen St t l d t h i l f h subj ect ed t o floods
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-
g gat hering syst em - provide warning g y p g t o m onit or prevent ion & m it igat ion syst em s.
ht t p: / / w w w.nfrm p.us
Pr e pa r a t ion Pr e pa r a t ion - Com m unicat ion, Com m unicat ion,
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 - rest orat ion. rest orat ion.
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 ySt ream s/ Rivers are t he m ain causes of floods.
I ce j am s or land slides blocking st ream s; t t yphoons and cyclones also cause floods. h d l l fl d
Excessive rainfall com bined w it h inadequat e carrying capacit y of st ream s result ing in over carrying capacit y of st ream s result ing in over spilling of banks is t he cause for flooding in m aj orit y of cases.
Floods in I n dia
MOWR has assessed t he area liable t o floods as 35 m illion hect ares St at e Area liable t o Floods
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 p: / / w w w.m ow r.nic.in ht t / / i i
Flood H a z a r ds in I n dia
I n I ndia, syst em at ic planning for flood m anagem ent com m enced wit h t he launching of Nat ional Program m e com m enced wit h t he launching of Nat ional Program m e of Flood Managem ent in 1954.
During t he last 58 years, different m et hods of flood prot ect ion st ruct ural as w ell as non- st ruct ural have i l ll l h 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 works, channel im provem ent works, det ent ion basins et c.
Non- st ruct ural m easures - flood forecast ing, flood plain l fl d f fl d l zoning, flood proofing, disast er preparedness et c.
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 A live st orage of 177 billion cubic m et er creat ed so far in of 177 billion cubic m et er creat ed so far in
t he various reservoirs for irrigat ion, hydropower generat ion, drinking wat er et c. - help in reducing flood int ensit y by st oring part of t he flood wat ers in t hem . int ensit y by st oring part of t he flood wat ers in t hem
Flood H a z a r ds in I n dia
The flood m anagem ent m easures undert aken so far has provided reasonable degree of prot ect ion t o an has provided reasonable degree of prot ect ion t o an area of 16.5 m illion hect ares t hrough out t he count ry.
ht t p: / / wrm in.nic.in/ 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 im 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 Com m ission, Minist ry of Wat er Resources i i Mi i f W R has set up a h
net work of forecast ing st at ions covering all im port ant flood prone int erst at e rivers. p
The forecast s issued by t hese st at ions are used t o
alert t he Public and t o enable t he adm inist rat ive and engineering agencies of t he St at es/ UT's t o t ake engineering agencies of t he St at es/ UT's t o t ake appropriat e m easures.
Coordinat ion w it h I SRO, I MD & Tele- net works ,
N a t ion a l r e spon se m e ch a n ism
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
What about syst em / process capabilit ies? What about syst em / process capabilit ies?
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
Forecast ing and warning ( t echnology use) d ( h l )
Cont ingency planning
- – Food grains availabilit y Food 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 capacit y not t hought t hrough
Re fe r e n ce s Re fe r e n ce s
Akan, A.O. and Ant oun, E.N. ( 1994) . “ Runoff det ent ion for flood
volum e or erosion cont rol, J. I rr. and Dr. ASCE 12( 1) , 168- 178. volum e or erosion cont rol ” J I rr and Dr ASCE 12( 1) 168 178
ht t p: / / ndm a.gov.in/ ndm a/ guidelines.ht m l
ht t p: / / w w w .epa.gov/ oaint rnt / st orm w at er/ index.ht m
Subrahm anya, K( 2007) . Engineering Hydrology, Tat a McGraw- Hill, New Delhi, 294- 300
g
g, p , Rest on, USA
Chow , V.T., Maidm ent , D.R., and Mays, L.W. ( 1988) . Applied Hydrology, McGraw- Hill,I nc., New York y gy, , ,
Bedient , P.B.,Huber, C.W. ( 1988) . Hydrology and Flood Plain Analysis, Addison- Wesley Publishing Com pany
ht t p: / / wrm in.nic.in 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 ( www .w rm in.nic.in) I ndia ( w w w 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
m easures on w at ershed/ river basin scale?. m easures on w at ershed/ river basin scale?.
Prof. T I Eldho, Department of Civil Engineering, IIT Bombay
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 operat ions.
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 & relat ed issues?.
Dr. T. I. Eldho Dr. T. I. Eldho Professor, Professor, Department of Civil Engineering, Department of Civil Engineering, p p g g g g Indian Institute of Technology Bombay, Indian Institute of Technology Bombay, Mumbai, India, 400 076. Mumbai, India, 400 076. Email: Email: Email: Email: [email protected] [email protected] [email protected] [email protected]