Stormwater system, Integrated storm water management separate system water management, separate system, combined system, Urban flooding

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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 1

St or m W a t e r M a n a ge m e n t

1 1 1 1 1

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L31

com bined syst em , Urban flooding



Keywords:

St orm wat er runoff, syst em , St orm wat er runoff, syst em , harvest ing, m anagem ent , Urban flooding.

harvest ing, m anagem ent , Urban flooding.

2

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St orm w at er Runoff

 St orm w at er is rainwat er & m elt ed snow t hat runs off

st reet s, lawns, & ot her sit es.

Wh t t i b b d i t t h d it i

 When st orm w at er is absorbed int o t he ground, it is

filt ered & replenishes aquifers or flows int o st ream s/ rivers.

 I n urbanized areas, im pervious areas like pavem ent &

roofs prevent wat er from nat urally soaking int o ground.

 Wat er runs rapidly int o st orm drains sewer syst em s &  Wat er runs rapidly int o st orm drains, sewer syst em s, &

drainage dit ches and can cause: D/ s flooding ; St ream bank erosion; I ncreased t urbidit y, Habit at dest ruct ion; Changes in t he st ream flow hydrograph; Com bined

Changes in t he st ream flow hydrograph; Com bined sewer overflows; I nfrast ruct ure dam age &

Cont am inat ed st ream s, rivers, & coast al wat er

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St or m w a t e r H a r ve st in g

 St orm wat er - concern for t he volum e and t im ing of runoff

w at er (flood cont rol & wat er supplies) & ot her relat ed w at er (flood cont rol & wat er supplies) & ot her relat ed

wat er pollut ion.

 St orm wat er is also a resource of readily available wat er.

h f h h

 Techniques of st orm wat er harvest ing w it h point source

wat er m anagem ent & purificat ion, can pot ent ially m ake urban environm ent s self sust aining in t erm s of wat er.

 St or m w a t e r h a r ve st in g is t he collect ion, accum ulat ion,

t reat m ent or purificat ion, & st oring for it s event ual reuse. I t can also include ot her cat chm ent areas from m an m ade

 I t can also include ot her cat chm ent areas from m an m ade

surfaces, such as roads, or ot her urban environm ent s such as parks, gardens & playing fields.

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St or m w a t e r M a n a ge m e n t

 Managing t he quant it y & qualit y - " St orm w at er

Managem ent ”

 " The t erm Best Managem ent Pract ice ( BMP) is oft en

used t o refer t o bot h st ruct ural or engineered cont rol devices & syst em s ( e.g. y ( g ret ent ion pondsp ) t o t reat )

pollut ed st orm wat er, as well as operat ional or procedural pract ices.

 There are m any form s of st orm wat er m anagem ent &  There are m any form s of st orm wat er m anagem ent &

BMPs, including:

• m anage st orm wat er t o cont rol flooding and erosion;

& t l h d t i l t t

• m anage & cont rol hazardous m at erials t o prevent release of pollut ant s t o environm ent ( source cont rol) ;

• plan and const ruct st orm wat er syst em s so t hat

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p y

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St or m w a t e r M a n a ge m e n t …

• Acquire and prot ect nat ural wat erways where t hey st ill exist or can be rehabilit at ed;

st ill exist or can be rehabilit at ed;

• Build " soft " st ruct ures such as ponds, swales or

wet lands t o work wit h exist ing or " hard" drainage st ruct ures such as pipes and concret e channels; st ruct ures, such as pipes and concret e channels;

• Revise current st orm wat er regulat ions t o address com prehensive st orm wat er needs;

• Enhance and enforce exist ing ordinances t o m ake sure • Enhance and enforce exist ing ordinances t o m ake sure propert y owners consider t he effect s of st orm wat er

before, during & aft er developm ent of t heir land;

Ed i b h i i ff

• Educat e a com m unit y about how it s act ions affect

wat er qualit y, & what it can do t o im prove it ; and • Plan carefully t o creat e solut ions before problem s

6 6

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Why Manage St orm w at er?

 Urbanized areas: More im pervious areas - Effect s of

st orm wat er

 Road flooding: accident s, washout s, driver delays.

 Building & propert y flooding: st ruct ural & propert y

dam age sewer backup foundat ion set t lem ent dam age, sewer backup, foundat ion set t lem ent , devalued propert ies.

 Environm ent al dam age.

 Ut ilit y service int errupt ions.

 I ncreased clean- up cost s, healt h hazards, personal

inconvenience, increased insurance cost s. inconvenience, increased insurance cost s.

 Solu t ion s: Concret e, St eel & HDPE pipe, Concret e

st ruct ures, Swales and ponds

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Why Manage St orm wat er?

 Manage large am ount of st orm wat er t o avoid flooding &

ot her inconveniences.

T dit i l t t t d i f d

 Tradit ional st orm w at er m anagem ent design - focused on

collect ing st orm wat er in piped net works & t ransport ing it off sit e as quickly as possible, eit her direct ly t o a st ream or river, t o a large st orm wat er m anagem ent facilit y

( basin), or t o a com bined sewer syst em flowing t o a wast ewat er t reat m ent plant . p

 Low im pact developm ent ( LI D) & wet weat her green

infrast ruct ure address t hese concerns t hrough a variet y of t echniques including st rat egic sit e design m easures t o t echniques, including st rat egic sit e design, m easures t o cont rol sources of runoff, & t hought ful landscape planning.

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I nt egrat ed St orm w at er Managem ent

 I nt egrat ed wat er m anagem ent ( I WM) of st orm wat er

-address m any of t he issues affect ing t he healt h of wat erways & wat er supply challenges facing t he wat erways & wat er supply challenges facing t he m odern urban cit y.

 I WM- S know n as low im pact developm ent in USA, or

Wat er Sensit ive Urban Design ( WSUD) in Aust ralia.

 I WM has t he pot ent ial t o im prove runoff qualit y, reduce

t he risk & im pact of flooding & deliver an addit ional t he risk & im pact of flooding & deliver an addit ional wat er resource t o augm ent pot able supply.

 Developm ent of m odern cit y oft en result s in increased

dem ands for wat er supply due t o populat ion growt h dem ands for wat er supply due t o populat ion growt h

 Alt ered runoff predict ed by clim at e change has

pot ent ial t o increase t he volum e of st orm wat er t hat can

9 9

p

cont ribut e t o drainage & flooding problem s.

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I nt egrat ed St orm w at er Managem ent

 I WM offers several t echniques including: st orm wat er

harvest ( reduce am ount of wat er causing flooding) , harvest ( reduce am ount of wat er causing flooding) ,

 infilt rat ion ( t o rest ore t he nat ural recharge of

groundwat er) ,

b f l b ( d )

 biofilt rat ion or bioret ent ion ( e.g., rain gardens) t o

st ore & t reat runoff & release it at a cont rolled rat e t o reduce im pact on st ream s & wet land t reat m ent s ( t o st ore, cont rol runoff & provide habit at in urban areas) .

 I WM - in it s infancy & brings t oget her elem ent s of

drainage science ecology & a realizat ion t hat drainage science, ecology & a realizat ion t hat t radit ional drainage solut ions t ransfer problem s furt her d/ s t o t he det rim ent of our environm ent & precious wat er resources

10 10

precious wat er resources.

Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

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Low I m pact Developm ent

( LI D ) :

LI D i l h d f i h h

 LI D: aim s t o rest ore nat ural wat ershed funct ions t hrough

sm all- scale t reat m ent at t he source of runoff. The goal is t o design a hydrologically funct ional sit e t hat m im ics pre-developm ent condit ions.

 LI D – Land developm ent – w orks wit h nat ure t o m anage

st orm wat er as close t o it s source as possible st orm wat er as close t o it s source as possible.

 LI D principles – preserve & recreat e nat ural landscape

feat ures, m inim ize effect ive im perviousness t o creat e

f t i l & li it d i t h t t t t t

funct ional & appealing sit e drainage t hat t reat st orm w at er as source.

 Pract ices – bioret ent ion facilit ies, rain gardens, veget at ed , g , g

rooft ops, rain barrels & perm eable pavem ent s.

 LI D – w at er m anaged in a way t hat reduces im pact of built

area & prom ot es nat ural wat er m ovem ent

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LI D & Green I nfrast ruct ure

 LI D rest ore a wat ershed’s hydrologic ecological funct ions  LI D – a sust ainable st orm wat er pract ice

Green I nfrast ruct ure refer t o syst em s & pract ices t hat

 Green I nfrast ruct ure - refer t o syst em s & pract ices t hat

use or m im ic nat ural processes t o infilt rat e, evapo-t ranspiraevapo-t e ( reevapo-t urn of waevapo-t er evapo-t o evapo-t he aevapo-t m osphere eievapo-t her

h h b l )

t hrough evaporat ion or by plant s) , or reuse st orm wat er on t he sit e where it is generat ed.

 Green infrast ruct ure-Green infrast ruct ure used at a wide range of landscape used at a wide range of landscape

scales in place of, or in addit ion t o, m ore t radit ional

st orm wat er cont rol elem ent s t o support principles of LI D.

Wet Weat her Green I nfrast ruct ure: encom passes

 Wet Weat her Green I nfrast ruct ure: encom passes

approaches & t echnologies t o infilt rat e, evapot ranspire,

capt ure, & reuse st orm wat er t o m aint ain or rest ore nat ural

h d l

12 12

hydrology

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Benefit s of LI D & Green I nfrast ruct ure

 Social, econom ic & environm ent al benefit s include:

 Socia l: Reduct ion in urban heat island effect Provides  Socia l: Reduct ion in urban heat island effect , Provides

“ green j obs’/ ” green business” opport unit ies;

Educat ional inform at ion provided t hrough st reet kiosks; Crim e reduct ion ; Healt h benefit s t hrough walking

Crim e reduct ion ; Healt h benefit s t hrough walking, biking, running t rails

 Econ om ic: Energy cost reduct ion using wind powered

LED light ing; Wat er conservat ion ; Green Ent erprise Business Opport unit ies

 En vir on m e n t a l: Carbon sequest rat ion; I m proved  En vir on m e n t a l: Carbon sequest rat ion; I m proved

wat er qualit y t hrough 90% capt ure of st orm wat er;

Carbon foot print reduct ion; Recycling & beneficial use.

13 13 Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

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Wat ershed Based St orm wat er Managem ent .



Goa ls:

Reduct ion of flood dam age t o life & propert y.

 Minim izat ion of st orm wat er runoff from new

developm ent .

 Reduct ion of soil erosion from const ruct ion act ivit ies.

I f d t t t f ilit i i l di

 I nsurance of adequat e st orm w at er facilit ies, including

culvert s, bridges, & ot her inst ream st ruct ures.

 Maint enance of groundwat er recharge.g g

 Prevent ion/ reduce of non- point st orm wat er pollut ion.

 Maint enance of surface wat ers t o ensure t heir

bi l i l & t t t f t i

biological & st orm w at er m anagem ent funct ions,

 Prot ect ion of public healt h & welfare, t hrough

operat ion & m aint enance of st orm wat er syst em s.

14 14

p y

Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

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Wat ershed Based St orm wat er Managem ent

 Pr in ciple s:

 1. Views regulat ory com pliance as a m inim um

requirem ent for accept ance.

 2. Requires a st orm wat er m anagem ent plan

considering wat ershed- wide needs considering wat ershed wide needs

 3. Focuses on achieving good environm ent al result s

for t he wat ershed in a cost - effect ive m anner

 4. I nt egrat es st orm wat er plans int o proj ect

developm ent and proj ect feat ures.

 5. Uses collaborat ive part nerships t o leverage and  5. Uses collaborat ive part nerships t o leverage and

deliver a com binat ion of wat ershed im provem ent s.

 6. A coordinat ed m it igat ion/ enhancem ent st rat egy.

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St orm w at er Cont rol Measures

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S

t orm wat er Managem ent

t orm wat er Managem ent –

– Separat e Syst em

Separat e Syst em

P ll d ff d h h

 Pollut ed st orm w at er runoff - t ransport ed t hrough

Municipal Separat e St orm Sewer Syst em s, from which it is oft en discharged unt reat ed int o local w at er bodies.

 To prevent harm ful pollut ant s from being w ashed or

dum ped int o w at er bodies, appropriat e pollut ion cont rol m easures should be developed

cont rol m easures should be developed.

 Separat e syst em s are com prised of t w o independent

piping syst em s: one syst em for " sanit ary" sewage

( i f h & b i ) d

( i.e., sewage from hom es & businesses) and one syst em for st orm wat er

Wast e

17 17

www.dcwasa.com / wast ewat er_collect ion/ css/

Wast e wat er t reat m ent plant

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S

t orm wat er Managem ent

t orm wat er Managem ent –

– Com bined Syst em

Com bined Syst em

 A com bined sewer syst em conveys bot h sanit ary  A com bined sewer syst em conveys bot h sanit ary

sewage & st orm wat er in one piping syst em

 During norm al dry weat her condit ions, sanit ary wast es

collect ed in t he com bined sewer syst em are divert ed t o t he Wast ewat er Treat m ent Plant .

 During periods of significant rainfall t he capacit y of a  During periods of significant rainfall, t he capacit y of a

com bined sewer m ay be exceeded - let t he excess

w w w.greenhighwayspart nership.org www.dcwasa.com / wast ewat er_collect ion/ css/

wat er t reat m ent plant

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b

i

ff

Ur ba n iz a t ion Effe ct s &

Floodin g

g

 Nat ural surface is covered by art ificial

st ruct ures

Urbanized  I t increases im pervious areas

 Channel charact erist ics of shape,

slope & roughness- bet t er known

Rural wat ershed wat ershed

Discharge

slope, & roughness- bet t er known

 Changes flow pat t ern & qualit y of runoff

is also influenced Tim e

 Est im at ion of losses is sim plified

 I t leads t o higher peak flow and short er t im e

t o peak and causes t he inundat ion problem at t he low- lying areas and undesirable load t o t he downst ream areas

19 19

downst ream areas

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Ur ba n Floodin g - Ca u se s

 Met eorological fact ors: Rainfall; Cyclonic st orm s;

Sm all- scale st orm s; Tem perat ure; Snowfall and Sm all scale st orm s; Tem perat ure; Snowfall and snowm elt

 Hydrological fact ors: Soil m oist ure level; Groundwat er

di i i fil i i i Ch l

condit ions; infilt rat ion; im pervious cover; Channel condit ions; Tidal effect s et c.

 Hum an fact ors: Land use/ land cover changes; in  Hum an fact ors: Land use/ land cover changes; in

appropriat e drainage syst em s; occupat ion of flood plain areas; sudden release of wat er from dam s; clim at e change; urban m icro clim at e; indiscrim inat e clim at e change; urban m icro clim at e; indiscrim inat e wast e disposal et c.

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Ur ba n Flood Pr oble m s

 The im pact s m ay include loss of m oney, t em porary

disrupt ion t o t ransport at ion syst em s.

I i t it lif

 I nconvenience t o cit y life

 I t can also cause erosion and inst abilit y of soils on st eep

slopes t hreat ening houses. p g

 The ext rem e event s result in inundat ion for a

prolonged durat ion

 Heavy rainfall, t idal influences and lack of

adequat e drainage syst em is a serious problem affect ing on m any coast al cit ies

affect ing on m any coast al cit ies.

 Due t o t he com plexit y of t he problem , advanced

m odeling t ools are required.

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Ur ba n iz a t ion I m pa ct s



Modificat ion

of

flooding

charact erist ics

–

by

int roducing st orm drains



Rapid rem oval of wat er from t he drained area

decreases t he t im e and infilt rat ion



To delay t he Peak rat e of runoff

increasing an



To delay t he Peak rat e of runoff – increasing an

area’s st orage capacit y and delaying out flow



Runoff from st reet s t o drainage syst em

Flooding due t o

:

Lim it ed int ake capacit y of t he

drainage syst em ; I nsufficient capacit y of t he pipe

syst em

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Appr oa ch e s in Ur ba n H ydr ology



Em pirical Lum ped- Param et er Approach



Considerat ion of t he ent ire drainage area as a

single unit



Est im at ion of flow at only t he m ost

d

t

i t

downst ream point



Assum pt ion of t he rainfall is uniform ly

dist ribut ed in t im e and space over t he

wat ershed



Apply t echniques such as unit hydrograph



Apply t echniques such as unit hydrograph

t echniques

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Appr oa ch e s in Ur ba n H ydr ology

Physical – Process Approach:

I nvolves follow ing

st eps



Det erm ine a design st orm



Deduct losses from t he design st orm t o arrive

at an excess rainfall rat e



Det erm ine t he flow t o a gut t er or som e defined

h

l b

l

d fl

channel by overland flow equat ions



Rout e t hese gut t er flow t o m ain channel flow



Rout e t he flow t hrough t he principal

conveyance syst em

D t

i

t h

t fl

h d

h

24 24 

Det erm ine t he out flow hydrograph

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Measures for Reducing/ Delaying St orm

Runoff

Plant ing a high delaying grass

w w w.greenhighwayspart nership.org



Plant ing a high delaying grass



I ncrease forest cover



Det ent ion basins

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Ca se St u dy: St or m w a t e r D r a in a ge for a n

Ur ba n Ar e a :

 St udy area: A Housing Colony – Sant acruz Mum bai

 To st udy t he act ual sit uat ion of t he flooding problem in a  To st udy t he act ual sit uat ion of t he flooding problem in a

low lying urban area subj ect ed t o t idal effect s and suggest m easures.

l h ff d b f fl d

 Present ly t he area is affect ed by frequent flooding in

m ost of t he m onsoon season as t his area is low- lying com pared t o t he nearby areas.

 Pr e se n t st a t u s of t h e dr a in a ge syst e m

 Two subm ersible pum ps ( capacit y of 10 HP each)

pum ping t he st orm wat er t o t he road drainage syst em pum ping t he st orm wat er t o t he road drainage syst em

 A 900 m m diam et er pipe ( slope of 1 in 1000) draining

direct ly t o t he Mit hi River.

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Present Drainage Syst em Capacit y

• The Mit hi River is passing nearby and t he drainage syst em drains int o t he river, which is subj ect ed t o syst em drains int o t he river, which is subj ect ed t o t idal effect .

• When t he wat er level rises in t he river and high t ide occurs t he out fall of drain is subj ect ed t o t idal effect s occurs t he out fall of drain is subj ect ed t o t idal effect s and consequent flooding.

• During t he year 2004 a new 900 m m diam et er

pipeline was laid t o solve t he flooding problem and pipeline was laid t o solve t he flooding problem and t hat year t he area was not subj ect ed t o flooding. • But in 2005, highest ever recorded rainfall occurred

d i h d h l

during t he m onsoon and t he area w as severely affect ed by floods.

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Present drainage system capacity

 St orm wat er discharge t hrough t he pum ping syst em

Q = 0.051 m3_{/ s}

 St orm wat er discharge t hrough t he 900 m m diam et er

pipe drain Q = 0.492 m3_{/ s.}

 Tot al drainage capacit y of t he present syst em  Tot al drainage capacit y of t he present syst em

0.543 m3_{/ s.}

 Rat ional form ula:

Q = CiA;

C – runoff coefficient  Rat ional form ula:

Q

CiA;

C runoff coefficient

= 1.0; Q – 0.543 m 3/ s; A – area t o be drained = 18 acres = 7.28 ha = 72875 m2; _{i - rainfall int ensit y =}

?? m m / hr ?? m m / hr.

From t he above calculat ion it is found t hat t he syst em is capable of discharging only 25 m m / hr rainfall

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Drainage Problem ..

 The m axim um hourly rainfall int ensit y in m ost of t he

year is m ore t han 25 m m / hr

 During t he m onsoon River overflows and in addit ion if  During t he m onsoon, River overflows and in addit ion if

t he heavy rainfall happens sim ult aneously wit h t he rising t ide a reverse flow occurs leading t o heavy flooding sit uat ion in t he area

flooding sit uat ion in t he area.

 Problem in select ing t he Design Crit eria

– Unavailabilit y of adequat e nat ural slope t o Unavailabilit y of adequat e nat ural slope t o facilit at e gravit y flow

– Tidal effect s encount ered at t he exit point

L k f id i d i

– Lack of space t o provide appropriat e drainage arrangem ent s since t he ground levels of

surrounding area had been raised m uch higher

30 30

t han t hose of t his colony.

(31)

D isch a r ge t o be dr a in e d by t h e syst e m for

(32)

Recommendations

 The present exist ing ground level has t o be increased

at least 60 cm in t he lower levels of t he low lying area, so t hat an adequat e slope is available for t he area, so t hat an adequat e slope is available for t he proposed new drain.

 A sm all gut t er all along t he int ernal road of t he area

leading t o t he lowest point Since t he exist ing 900 m m leading t o t he lowest point . Since t he exist ing 900 m m pipe is alm ost at ground level, it is advisable not t o

have cross connect ion inlet s ot her t han t he exist ing

l h 900 d d

inlet s t o t his exist ing 900 m m diam et er pipe drain.

 Ent ry of st orm wat er from t he surrounding areas

needs t o be prevent ed needs t o be prevent ed

 The cross connect ions t o t he nearby Draining Nullah

has t o be cut off as t he lat t er has a high invert level, which would give rise t o a reverse flow

32 32

which would give rise t o a reverse flow.

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Re fe r e n ce s



Am erican Societ y of Civil Engineers and Wat er Environm ent Federat ion ( ASCE and WEF) . 1998. Urban Runoff Qualit y

Managem ent . WEF Manual of Pract ice No. 23, ASCE Manual and

Report on Engineering Pract ice No. 87.

 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  ht t p: / / wrm in nic in

 ht t p: / / wrm in.nic.in

 Nat ional Research Council of t he Nat ional Academ ies ( NRC) . 2008.

“ Urban St orm wat er Managem ent in t he Unit es St at es.” The Nat ional Academ ies Press Washingt on DC

Nat ional Academ ies Press. Washingt on, DC.

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Tu t or ia ls - Qu e st ion !.?.



Crit ically st udy t he st orm w at er m anagem ent

issues in I ndia What are t he m aj or

issues in I ndia. What are t he m aj or

problem s in im plem ent ing appropriat e

st orm w at er m anagem ent syst em s in I ndian

g

y

cit ies like Mum bai/ Kolkot t a?.

h t t p:/ / n dm a .gov.in / n dm a / gu ide lin e s.h t m l



Com pare t he st orm wat er m anagem ent

pract ices in USA, UK and I ndia and propose

bet t er m anagem ent pract ices for I ndian

Cit ies.

(35)

Se lf Eva lu a t ion - Qu e st ion s!.

 Discuss st orm wat er runoff & param et ers influencing on

wat ershed basis wat ershed basis.

 What is t he “ Best Managem ent Pract ices” relat ed t o

“ St orm w at er Managem ent ” ?.

 Discuss I nt egrat ed St orm wat er Managem ent pract ices.

 What are t he goals & principles of wat ershed based

S ?

St orm wat er Managem ent ?.

 Different iat e bet ween “ Separat e” & “ Com bined”

st orm wat er m anagem ent syst em st orm wat er m anagem ent syst em .

 What are im port ant m easures for delaying st orm runoff?

(36)

Assign m e n t - Qu e st ion s?.

g

Q

 I llust rat e various st orm wat er harvest ing t echniques.

 Why we have t o m anage st orm wat er?.y g

 Discuss t he feat ures of “ Low I m pact Developm ent &

Green I nfrast ruct ure” wit hin t he perspect ive of

t t t

st orm w at er m anagem ent .

 I llust rat e im port ant st orm wat er cont rol m easures.

 What are t he im port ant effect s of urbanizat ion on  What are t he im port ant effect s of urbanizat ion on

runoff?.

 Discuss t he im port ant causes of urban flooding.p g

 Different iat e bet ween “ em pirical lum ped param et er

approach” and “ physical process approach” in urban

h d l

36 36 36 36

hydrology.

(37)

Un solve d Pr oble m !.



What are t he im port ant st orm w at er

m anagem ent problem s in your w at ershed area?.

(38)

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

38 38

Email:

Email: [email protected]@iitb.ac.in

Phone: (022)

Phone: (022) –– 25767339; Fax: 2576730225767339; Fax: 25767302

http://www.