drainage/storm water network design for a small community in ilorin

8/13/2019 DRAINAGE/STORM WATER NETWORK DESIGN FOR A SMALL COMMUNITY IN ILORIN.

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DRAINAGE/STORM WATER NETWORK DESIGN FOR A SMALLCOMMUNITY IN ILORIN.

COMPUTER AIDED DESIGN (CVE 656)

By

OKEKE, T.C. (12/68GE004) Department o C!"!# En$!neer!n$

Un!"er%!ty o I#or!n& N!$er!a

CVE 656 Cou !" #"$%u " & Dr S.A Ra'!

OCT& ()*+


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DRAINAGE/STORM WATER NETWORK DESIGNS FOR A SMALL COMMUNITY IN ILORIN.

ABSTRACT

Overland flow through a surface is usually channeled to either a surface drain or and underground sub-surface drain. In this study, kulenda housing estate Ilorin was designed using open surface drain for itsinternal roads and storm water underground drain for the external roads. Flow discharge from Ollotaroad (i.e internal road with highest discharge rate was used in this design for the internal road network.!ational method was used for the computation of flow discharge. "he hydrological and hydraulicanalysis of the estate culverts, storm drains was done using both visual basic and Hy8_7_3 sof !"#$.!esults obtained shows a #$$$mm x %$$mm section for the open surface drain and the storm waterdesign shows varying pipe diameters ranging from &'$mm to #'$$mm. omparing the values obtainedwith established standards authenticates the ade)uacy of provided sections.

%.& INTRODUCTION

*rban drainage systems consist of three parts+ the overland surface flow system, the sewer network,and the underground porous media drainage system ( en and kan,# %/ . In the urban environment,storm water drainage systems are provided to convey runoff from developments in a safe, convenient,and environmentally conscious manner. Inherent in this philosophy is the analysis of rainfall events(storms that result in both 0minor1 and 0ma2or1 storm water flows ( ity of anterbury,# ' . In thisdesign, the 0minor1 storm flow was channeled through the open surface drains while the 0ma2or1 stormwater was drained using the underground storm water drain. ll storm drain designs is be based on anengineering analysis which takes into consideration runoff rates, pipe flow capacity, hydraulic grade line,soil characteristics, pipe strength, potential construction problems, and potential runoff treatmentissues.(345O",6$#$ .

'.& DESCRI(TION OF THE STUDY AREA

7y study area is the 8ulende 9ousing :state (phase III Ilorin. It is located along the ;ebba road axis. "hearea slopes from the east to the west and from the north to the south. "he soil type is a clayey loamysoil. "he layout of kulende estate was drawn to a scale of #+6$$$. "he topographical map of my studyarea is shown in fig #.$ below.


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F)* %.&."he "opgraphical 7ap of 8ulende :state Ilorin indicating the various streets and the contourslopes alignments.

3.& LITERATURE RE+IEW.

4everal designs and literature publications on the design of storm water have been undertaken byseveral researcher and engineers. good knowledge of the hydrology of surface water flow is a

prere)uisite for the design of storm drains and channels. ;ohn !ational method, 8inematic wave method, and 4 4 unit hydrograph method. "he rational method wasdeveloped by 8uichling (#%% for estimating design discharge for small urban watersheds. "he rationalmethod has become the basis for design of many small watershed hydraulic structures. "hompson(6$$= defines the rational method as a simple formula that relates runoff producing potential of thewatershed, the average intensity of rainfall for a particular length of time (the time of concentration ,

and the watershed drainage area. "he rainfall intensity computation is based on a time of concentrationwhich "hompson (6$$= defined as the time re)uired for a parcel of runoff to travel from the mosthydraulically distant part of a watershed to the outlet.

,.& DESIGN METHODOLOGY

"he method of approach adopted for the design of 8ulenda :state is divided into the followingcategories namely>


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4.1 Preliminary survey: "his involves a site visit to the area to determine the soil type and land slopesin the estate.

4.2 Data collection : !elevant data like the topographical map and the rainfall intensity- duration-Fre)uency chart for Ilorin were obtained from the relevant organi?ations.

4.3 Hydrological Design: "he catchment flow rate was determined using the rational method which isstated "s / . .....E- (i

3here, is the Coefficient of runoff which represents the fraction of rainfall converted torunoff.("hompson, 6$$= . ppropriate values for coefficient of runoff are shown in the table#.$. is theRainfall intensity which is expressed as the average rainfall intensity in mm@hr for a selectedreoccurrence fre)uency and for duration e)ual to the time of concentration of the watershed("hompson, 6$$= . and A is the Area of waters ed! in ectares .

"he "ime of concentration was obtained using kirpich formulae T 0 &1&&782 L&.77/S4&1385 6E- ))3here+ T A time of concentration in mins. L A length of water shed area (ft . S A 4lope of water shadewhich was obtained using the slope formulae. Design return #eriod of #$ years was used in thisanalysis.

"able #.$. !unoff oefficients for !ational 7ethod. ( dopted from F93 , 6$$# 1S) *>$ F"?)>y A#$" $./$ - $.'$M > ) U ) @ D$ " ;$= $.&$ - $.B$M > ) U ) @ A " ;$= $.B$ - $.='S < #>) * A#$" $.'$ - $.=$

S #$$ s1

As ;"> ) $.=$ - $. 'Co #$ $ $.%$ - $. 'B#) $.=$ - $.%'D#) $s " = W"> !"ys $.=$ - $.%'Roofs $.=$ - $. '


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4.4 Hydraulic design: ppropriate sections were computed using design formulas obtained from thetable 6.$ below. "his values are based on the assumption that

2 , ."able6.$ C 9ydraulic 4ections Dalues ( ! " 2 # ! " .C#osss$ )o

A#$" A4 W$ $=$#)?$ $# (4

Hy=#" >)R"=) s R4

To!)= ; T4

Hy=#" >)=$ ; D4

S$ )oF" o# F4

T#" $ o)= $%& 2'%& 2 ( %&& &(

&$.)2

R$ " *>$ 2 $ (' 2

2' * 2 $.) T#)" *>$ $ 2'%2 +

( '%2 2'

2 %22$.)

("#""

($

2 %2 &%2 2 2'%& -

2 $.)

%& S$?) )# >$ - $

2 -

2 2' -

( - $.)

(

"able /.$+ 5ifferent Dalues of 7annings !oughness oefficient .

Ty $s of C;" $> >) ) * Ro *; $ss Co$ff) )$ @S?oo ; o #$ $ $.$#6S?oo ; "s ;"> $.$#'E"# ; $.$6$Ro $.$/'G#"ss " = B# s; $.$'$D )>$ I#o ) $ $.$#/Co## *" $= s $$> ) $ $.$6&Co## *" $= >"s ) ) $ $.$6&

"he following are the hydrological and hydraulic considerations+

"he peak discharge obtained using the rational formulae served as design capacity for the pipesand drains.

"he hydraulic analysis of flow in the culvert, open channel and closed conduit drains was doneusing the Hy8_7_3 sof !"#$.

"he estate was designed to conform to the existing ground slope. !ectangular sections were used for the open surface drains while circular sections were used for

the storm water drain. "he manningEs e)uation was used in the determination of the si?es of the pipes and drains.

"hese computations of the various drain si?es were done using the visual basic programminglanguage.


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"he flow area, wetted perimeter and the hydraulic radius were derived from design formulas intable 6.$.

"he storm sewers were designed using a minimum cleansing velocity of $.Bm/@s

5.& THE DRAINAGE DESIGN.

$.1 Hydrological and Hydraulic Analysis for t e o#en c annel drainage system.

"he following visual basic codes were used in the computation of the time of concentration+


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Fig 6.$. !ainfall Intensity 5uaration urve for Ilorin 7etropolis

"able &.$+


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Ilorin3 :tsu


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"able '.$. Hy8_7_3 sof !"#$ 4ummary sheet for the critical culvert across :. dewumi !oad

C > $#D)s ;"#*$fs4

H$"=!" $#E>$ " )of 4

I >$o #o>=$ ;f 4

O >$o #o>D$ ;f 4

C#) ) ">D$ ;f 4

O >$+$>o ) yf /s4

I >$E>$ " )of 4

O >$E>$ " )of 4

C > $#L$ * ;f 4

&.&& %=.%/ $.$$ $.$$ $.$$ $.$$ =B.#B %=.$ /$,.38 %%./6 $.& #.6= $./$ &.B&. 7 %%.'% $.=' #. ' $.&% =.66%,.5& %%.%# $. % 6.'# $.B& #$.$%% .33 % .$6 #.# /.$$ $.=% #$.',.% % .6# #./% /.&' $. $ ##.=$' .&& % ./ #.'B /.%% #.$6 #6.6/33.83 % .'% #.=' &./$ #.#/ #6.B#38. % .=% #. ' &.=' #.6& #6.=/,3.5& % . % 6.#& '.6% #./& #/.66,8.33 $.#= 6./& B.B% #.&/ #/.'$

Fig&.$ !ating urve for the ulvert through :. dewumi.

$.4 Design of storm water drain in t e area.

"he external road network which includes roads like :. dewumi, 7ohammadu Muhari and7ohammed Gawal roads were designed using the storm water drainage. "he manning e)uation wasused in the determination of the best hydraulic section for the storm water drains.

88

89

90

91

92

93

94

95

96

97

98

99

100

0 20 40 60 80 100 120 140 160 180 200

Performance CurveCulvert: Culvert 2

H e a

d w a t e r

E l e v a t i o n

( f t )

Total Discharge (cfs)

Inlet Control Elev Outlet Control Elev


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For a full flow pipe+

0 MN4O

,CFD GNO.PQRSTUTQTUFV W CFD X UFT@ BCFFUFVYS :ZQCTU@F [ US\E.E(+=+ #6]74

5_. :ZF UUU.

Imputing the obtained flow discharges for :. dewumi road into Hy8_7_3 sof !"#$@ the stagedischarge graph and the flow velocities were obtained.

"able B.$. Hy8_7_3 sof !"#$ 4ummary sheet for the underground storm water drain along :. dewumi!oad.

S$!$#D)s ;"#*$fs4

H$"=!" $#E>$ " )of 4

I >$o #o>=$ ;

f 4

O >$o #o>D$ ;

f 4

No#?">D$ ;f 4

O >$+$>o ) yf /s4

I >$E>$ " )of 4

O >$E>$ " )of 4

S$!$#L$ * ;f 4

&.&& = .=/ $.$$ $.$$ $.$$ $.$$ = .=/ ='.// #%$$%3.& %#.$ $.%6 #.6= $.== &.'&' .& %#.B #./$ #. ' #.#% '.6B3 .& %6.6& #.=$ 6.'# #.'/ B./$5'.& %6.=/ 6.$' /.$$ #.%' B. #5 .& %/.# 6./B /.&' 6.#= =.&=78.& %/.B6 6.B& /.%% 6.&% =.8.& %&.$& 6.% &./$ 6.%6 %.&%&,.& %&.&% /.#& &.=' /.66 %. &%%7.& %'.$6 /./% '.6% &.#= .&$

%3&.& %B./% /.B6 B.B% &.#= .%&

Fig'.$ !ating urve for the underground storm water drain along :. dewumi !oad.

80

85

90

95

100

105

0 50 100 150 200 250

Performance CurveCulvert: Culvert 2

e a w a e r

e v a i o n ( )

Total Discharge (cfs)

Inlet Control Elev Outlet Control Elev


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Fig &.$ *nderground 4torm 3ater 5rain 4i?es for :. dewumi, 7ohammed Muhari, 7ohammed Gawal.

"he table below shows the computed discharge and ring diameter for the external roads.

"able =.$+ Flow summary sheet of storm water drains for :. dewumi, 7 Muhari, and 7 Gawal !oads.

Ro"=s S>o $ ?/?4 D)s ;"#*$ ?3/s4 F>o! +$>o ) y?/s4

D$s)* $=S$ )o

(#o )=$=S$ )o

E.A A=$! ?) $.$$& /.'% 6.'& #/B$ #'$$Mo;"??$=B ;"#)

$.$6% $.' 6.% &/% &'$

Mo;"??$=L"!">

$.$6 $.% /.B% '&/ B$$

omparing the flow values obtained shown in table =.$ with those in table %.$ and table .$ confirmsthe ade)uacy of the estimated flow velocity.

"able %.$ cceptable flow velocities for pipes and box culverts

F>o! Co =) )o A $M) )? ? ?/s4

D$s)#"$M) )? ? ?/s4

D$s)#"$M" )? ? ?/s4

A $M" )? ? ?/s4

("# )">>y f >> $.= #.6 &.= =.$F >> $.B #.$ &.$ B.$4ource+ GO H ity council 6$$&

"able .$+ cceptable pipe grades for pipes flowing full.() $ D)"?$ $# M" )? ? G#"=$ M) )? ? G#"=$3&& 6$ $.'375 #' $.&,5& ## $./5'5 .$ $.6'&& =.' $.6$75 B.' $.#$75& '.' $.#'&& &.' $.#6


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drainage/storm water network design for a small community in ilorin

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