Design of Roadside Drainage - Atlantic International University...iii Abstract This thesis work is concerned with the design of roadside drainage, in Kabuga to Tudunyola area of Kano

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ALIYU ADAM MIKAIL UB57978SCI66988

Design of Roadside Drainage

(A case study of Kabuga to Tudunyola)

A final thesis presented to the academic department of the school of science and engineering

In partial fulfillment for the award of bachelor in civil engineering

ATLANTIC INTERNATIONAL UNIVERSITY

HONOLULU, HAWAII

Summer, 2020

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Acknowledgement

My sincere thank goes to Almighty Allah for his guidance and protection over my life. I’m

greatly indebted to Dr. Leonardo Salas my advisor for his understanding, patience, tolerance

and encouragement, right from the beginning to the end of my thesis. I will also like to thank

all the staff at AIU such as my former advisor Dr. Edward Lambert academic coordinator, Dr.

Jack Rosenzweig dean of academic affairs, Kimberly Diaz and Virginia Diaz academic tutors

for their contributions towards the completion of my program at AIU. I will also like to thank

and appreciate my loving friends, course mates and all civil engineering students who have

endured all engineering hurdles. Finally, I will like to thank my entire family, especially my

parents, brothers and sisters, for their contribution financially, academically and morally,

since I was born till to date. May Allah (SWT) reward them abundantly, throughout their life.

Certainly, some individuals have also contributed greatly to the successful completion of my

thesis. But their names may not be mentioned due to lack of space, their assistance is

hereby acknowledged.

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Abstract

This thesis work is concerned with the design of roadside drainage, in Kabuga to

Tudunyola area of Kano city. The thesis is meant to design an efficient, safe and economic

drainage system, so as to provide solution to the problems that are encountered. Several

design parameters, tables and constants were used. Among them are rainfall intense of

11.08mm/hr, catchment areas of 0.012,0.0235,0.025,0.03,04km2 for the subcatchments of

the various conduits. Run off coefficient (K) of 0.45. Therefore the resulting design

discharges are 0.525,1.07,1.14,1.36,1.82m3/s for conduits 1,2,3,4,5 which are the same for

conduits 6,7,8,9,10 respectively. By the results obtained from table 4.4 the result shows that;

what is obtained from the software is supposed to be used, for all conduits with the

exception to the conduit that appear in thirds and eighth line of the table. Moreover, the table

4.6 is summarized like this; the depth obtained using software in terms of conduits 1,2,3,6,7

and 8. While the ones gotten through manual design are higher in terms of conduits 4,5,9

and 10. Having completed the design, the required sections were provided for all the

conduits.

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TABLE OF CONTENT

Acknowledgement - - - - - - - - - ii

Abstract - - - - - - - - - - - iii

Table of contents - - - - - - - - - - iv

CHAPTER ONE

1.0 Introduction - - - - - - - - - 1

1.1 Historical background - - - - - - - - 2

1.2 Statement of the problem - - - - - - - 2

1.3 Aims and Objectives - - - - - - - - 2

1.3.1 Aims - - - - - - - - - - 2

1.3.2 Objectives - - - - - - - - - - 2

1.4 Scope of the thesis - - - - - - - - 3

1.5 Significant of the thesis - - - - - - - - 3

1.6 Methodology - - - - - - - - - 3

CHAPTER TWO

Literature Review

2.1 Introduction - - - - - - - - - 4

2.2 Types of drainage - - - - - - - - - 4

2.2.1 Subsurface Drainage - - - - - - - - 5

2.2.2 Surface Drainage - - - - - - - - 5

2.2.3 Cross Drainage - - - - - - - - - 5

2.3 Measures adopted for surface drainage - - - - - 6

2.4 Collection of surface water - - - - - - - 6

2.5 Classification of side drainage - - - - - - 6

2.6 Categories of drainage - - - - - - - - 7

2.6.1 Urban storm drainage - - - - - - - - 7

2.6.2 Highway drainage - - - - - - - - 7

2.6.3 Land drainage - - - - - - - - - 7

2.7 Effect of poor drainage system on infrastructures - - - 10

2.8 Essence and adequate drainage system - - - - - 10

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2.9 Maintenance of existing drainage system - - - - - 11

2.9.1 Type of water maintenance - - - - - - - 11

2.10 Culverts - - - - - - - - - - 11

2.10.1 Types of culvert flow - - - - - - - - 12

2.10.2 Culvert type and materials - - - - - - - 12

2.10.3 Selection of culvert type - - - - - - - - 13

2.11 Requirement of highway drainage system - - - - - 13

2.12 Design of surface drainage - - - - - - - 13

2.12.1 Hydrological analysis - - - - - - - - 13

2.12.2 Determination of runoff - - - - - - - 14

2.12.3 Hydraulic design - - - - - - - - 15

2.12.4 Time of concentration (tc) - - - - - - - 17

CHAPTER THREE

3.1 Drainage hydrology - - - - - - - - 19

3.2 Estimating runoff coefficient C - - - - - - - 20

3.3 Rainfall intensity [I] - - - - - - - - 21

3.3.1 Rainfall Intensity [I] - - - - - - - - 22

3.4 Catchment area - - - - - - - - - 23

3.5 Checking slopes at various locations using a profile leveling - - 26

3.6 Determination of runoff - - - - - - - 27

3.7 Longitudinal slope and side slope - - - - - - 29

3.8 Canal dimensions - - - - - - - - - 29

3.9 Freeboard (FB) and Top width (T) - - - - - - 29

3.10 Design using SWMM software - - - - - - - 29

CHAPTER FOUR

Presentation of Result

4.1 Design of side drainage and discussion - - - - - 48

4.1.1 Calculation of top width for conduits 1,2,3,6,7,8 - - - - 48

4.1.2 Calculation of top width for conduits 4,5,9 and 10 - - - - 49

4.2 Manual design - - - - - - - - - 50

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4.2.1 Design of conduits - - - - - - - - 52

4.3 Design of rectangular section - - - - - - - 67

4.3.1 Manual design method - - - - - - - - 68

4.4 Discussions - - - - - - - - - 78

CHAPTER FIVE

Conclusion and recommendation

5.1 Conclusion - - - - - - - - - 83

5.2 Recommendation - - - - - - - - - 83

Appendix I - - - - - - - - - - - 85

Appendix II - - - - - - - - - - - 86

Appendix III - - - - - - - - - - - 87

References - - - - - - - - - - - 89

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CHAPTER ONE

1.0 Introduction:

Drainage is the process of interception and removal of water from over, and under the

vicinity of the road surface. Drainage can be surface (where water is conveyed on the road

surface and drainage channels), or surface (water flows underneath the pavement

structure).

Surface and subsurface drainage of roads critically affects their structural integrity, life

and safety to the users, and is thus important during highway design and construction. Road

designs therefore have to provide efficient means for removal of this water; hence the need

for road drainage designs.

Drainage facilities are required to protect the road against damage from surface and

subsurface water. Traffic safety is also important as poor drainage can result in dangerous

conditions. Poor drainage can also compromise the structural integrity and life of a

pavement. Drainage systems combine various natural and a manmade facility e.g. ditches,

pipes, culverts, curbs to convey this water safely.

There are several drainage components that are fairly common in most drainage system.

Successful construction involves selecting the appropriate materials for collection,

conveyance, and discharge requirements of any drainage system. Attention to proper

capacity and durability of each drainage material is critical. The performance of any

drainage system will be improved by using good construction techniques and performing

routine periodic maintenance.

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Hence the aim of this work is to design an efficient drainage system along this road.

1.1 Historical background:

This road is located along Kofar Kabuga to Tudunyola. It is a paved road and is under the

Gwale Local Government Council. The width of the single carriage way is 7.7m.

1.2 Statement of the problem:

According to this problem of having a failed side drainage along this road, the soil

adjacent to both sides of the drainage has been eroded by the water flowing during the rain.

This affects the houses there to the extent of flooding into rooms; it also affects peasant

farmers due to their vegetable gardens subjected to erosion. Also because the water during

the rain is passing on the road, potholes have occurred on top of this road. Therefore a

drainage system has to be designed. However, the existence road along this street is

showing signs of failure, caused mainly by lacking of drainage. Also it is better to have good

method of designing a side drainage in order to overcome these problems arises on this

road.

1.3 Aims and Objectives:

1.3.1 Aims:

Aims of this thesis are to design efficient drainage systems along Kabuga to Tudunyola

road.

1.3.2 Objectives:

1- To determine the catchment area and the expect flow.

2- To determine the runoff into the drainage and discharge of water from the system.

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3- To propose and design an efficient drainage system.

1.4 Scope of the thesis:

The scope of the thesis is to design a drainage system along Kabuga to Tudunyola road.

1.5 Significant of the thesis:

The thesis when completed will solve the problem of over flooding around the settlement,

the outcome of this thesis shall help to propose the layout from the new side drainage in

order to fulfill its requirements as a drainage, such as a drain off excess water on shoulder

and pavement edge cause considerable damage and improve pedestrian safety using walk

ways near side drainage.

1.6 Methodology:

Site visiting: This involves carrying out reconnaissance survey for better understanding of

the problems and to know the instruments to be used.

Determination of runoff: This involves determining the catchment area, critical intensity of

storm and a constant depending upon the nature of the surface.

Determination of area of cross section and dimensions: This involves determining the

allowable velocity of flow and the quantity of surface water to be removed by the drainage.

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CHAPTER TWO

Literature Review

2.1 Introduction

Highway drainage is the process of interception and removal of water from over, under

and in the vicinity of the road pavement. Drains are used to carry away such unwanted

waters, sewage and any other unwanted liquids. Drains can be pipe, channel or trench;

lined or unlined; covered or opened.

Highway drainage is one of the most important factors in road design and construction. If

every other aspect of the highway design and construction is done well but drainage is not,

the road will quickly fail in use due to ingress of water into the pavement and its base.

The damaging effects of water in the pavement can be controlled by keeping water out of

places where it can cause damage or by rapidly and safely removing it by drainage

methods.

Improper drainage of roads can lead to;

1. Loss of strength of pavement materials

2. Mud pumping in rigid pavement

3. Stripping of the bituminous surface in flexible pavements

2.2 Types of drainage

Orr (2003) points out that there are basically three types of drainage applied to highways

these are:

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1. Subsurface drainage

2. Surface drainage and

3. Cross drainage

2.2.1 Subsurface Drainage

Subsurface drainage is concerned with the interception and removal of water from within

the pavement. Some of the sources of subsurface water include; infiltration through surface

cracks, capillary rise from lower layers, seepage from the sides of the pavement to mention

but a few.

Application of side slopes on the road surface, installing of drainage beds in the pavement

and use of transverse drains are some of the measures of effecting subsurface drainage.

2.2.2 Surface Drainage

Surface drainage deals with arrangements for quickly and effectively leading away the

water that collects on the surface of the pavement, shoulders, slopes of embankments, cuts

and the land adjoining the highway.

The main source of surface water in most places is precipitation in form of rain. When

precipitation falls on an area, some of the water infiltrates in to the ground while a

considerable amount remains on top of the surface as surface runoff.

2.2.3 Cross Drainage

When stream have to cross a roadway or when water from side drainage have to be

diverted to water course across the roadway, then a cross drainage work such as culvert or

small bridge is provided.

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On less important roads, in order to reduce the construction cost of drainage structures,

sometimes submersible bridges or courses way are constructed. During flood the water will

flow over the road.

2.3 Measures adopted for surface drainage

1. Proper cross slope should be provided for both pavement and shoulders

2. The sub-grade should be sufficiently above the highest level of ground water stable

or the natural ground level

3. Side drainage should have to be provided at edges of right-of-way where the road is

in embankment and the edge of the roadway in cutting

4. On hill roads, water may flow towards the road depending on the slope and rainfall

5. Catch water drains should be provided to intercept the flow down.

2.4 Collection of surface water

The water collected is lead into natural channels or artificial channels so that it does not

interfere with the proper functioning of any part of the highway.

Surface drainage must be provided to drain the precipitation away from the pavement

structure.

2.5 Classification of side drainage

There are different types of roadside drainage, classified according to the type of

construction, which is as follows;

- Trapezoidal surface drainage

- V – Shaped lined surface drainage

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- Rectangular surface drainage

- Semi circular surface drainage

2.6 Categories of drainage

Basically, there are three categories of drainages. These are urban storm drainage, land

drainage and highway drainage, (Orr 2003)

2.6.1 Urban storm drainage

This is the system of collecting storm water in the streets of a city and conveying it

through inlets to buried/ open conduits which finally carry it to a point where it can be safely

discharged into a stream, lake or ocean.

2.6.2 Highway drainage

A system of drainage which discharge surface and ground water freely and quickly away

from road or under the road without flooding or damaging the highway and adjacent areas.

2.6.3 Land drainage

This is the system of removing excess surface water from an area or a system of lowering

the ground water below the root zone to improved plant growth or reduces the accumulation

of soil sects. Primarily, there are two types of land drainage system:

Open drainage ditches

Open drainage ditches are shallow gutters provided to lead away-unwanted water. They

can be small ditches or large ditches; lined or unlined ditches. Small ditches can be

constructed manually using diggers and shovels or mechanically using ditching machines.

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Large ditches are often excavated using dragline and floating dredges. Construction of

drainage ditches is best if it’s as close to the most efficient cross section as possible.

They are constructed using concrete and block. The drainage network is used to drain

surface water during raining season.

A quick walk along the drain can give you good idea of the extent of the blockage.

Frequently, however open drains carry sewage as well as runoff. According to Chow V.T

(1978), the only way to serve hydraulic performance is to study the drain itself during rainfall.

Such a survey can find:

a- Overflow locations

b- Bottlenecks and high head losses in culverts

c- Obstructed entry to the drain, (inlet blockage, poor inlet design, or poor surface

grading).

Under drains

These are covered drains or buried drains under the earth to carry away unwanted water

to a designated point. Several materials are available for use. The most common ones are

unglazed clay-tiles or concrete pipes, perforated steel pipe and wooden box drain are also

used. Construction of under drains is achieved by excavating a mall trench, placing the

drains laterally end to end, joining the ends using method of jointing and covering with the

earth.

A more economical system of under-drain construction is using fabric and gravel drains.

These are constructed by excavating a small trench, lining the trench with a synthetic fabric,

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back filling with gravel, aping the fabric, back filling the trench with soil. The slope of under-

drain should not be less than 0.2% to provide a velocity of 0.3m/s when flowingly full to

avoid sediment deposit in the pipe. (Highway engineering manual vol.2) Components of

under drain drainage system include:

i. Drainage pipe:

Drainage pipe is available in rigid wall lengths. On individual lots most applications

requires fairly small diameter pipe (4 inches to 12 inches). The walls of pipe vary from thin

and corrugated to thick and solid. Each pipe type has some degree of flexibility over the

length, which has many advantages in slope application and some disadvantages. The

biggest disadvantage is that the installer must check the grade of the pipe to conform there

are no reverse slopes or low prints along the length of pipe which may reduce the

performance of the drainage system.

ii. Catchbasins and Manholes:

Drainage systems need a method to collect and concentrate water flow at a location,

catchbasins and manholes allow pipes coming from different directions and elevations to

converge at specific locations. Catchbasin and manholes can trap larger sediment and

debris allowing only drainage with fine sediment to enter pipes. Also, they can provide a

drop in elevation down a slope and dissipate the energy of pipe flows.

Catchbasins and manholes structure are commonly constructed of concrete a polyethylene

and have a number of lid options ranging from open gates to water tight construction.

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2.7 Effect of poor drainage system on infrastructures

Poor drainage around buildings can lead to wet basement, frost heaving problems, and

the build-up of hydrostatic pressure on basement floors, banks and retaining walls. A well

designed land drainage system can convert useless, poorly drained land to valuable building

sites or permit construction to be carried on during extended periods of wet weather.

Strom drainage facilities are required for most cities and rural areas and they are usually

very expansive. Drainage facilities take up to 25% of the total cost of highways. Improper

drainage of highways may result in collapse of the road under land. Abiola (1985) indicated

the importance of drainage to roads was presented, thus, for adequacy of its drainage

system. Water standing on highway is a danger to high-speed traffic which is accentuated

when freezing temperature occurs. Water seeping into the pavement and sub-grade levels

leads to the development of soft spots, which result in the breaking up of the road.

Poor drainage also leads to cracking, erosion, potholes, flooding and washout.

2.8 Essence and adequate drainage system

Water is a good friend but can also become an enemy when excess and uncontrolled.

When there is excess water, the excess has to be drained away through a desired route.

The main essence of adequate drainage can be:

a- To control flooding

b- To prevent erosion

c- To control water pollution

d- To prevent water logging

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2.9 Maintenance of existing drainage system

As the work involved in a drainage scheme does not terminate with the construction,

proper maintenance is importance to keep the system in operation and enable it to function

at all times. A large amount of dirt, leaves, refuse, sand, dead animals and other decays find

their ways into the drainage system and may therefore cause blockage to the drains, thus

preventing their proper functioning. As a result, maintenance efforts become an important

aspect.

2.9.1 Type of water maintenance

There are three types of water maintenance:-

i- Preventive,

ii- Routine (regular) and

iii- Corrective (emergence) maintenance.

Presently, maintenance of drainage systems in Kano falls in corrective type. That is, the

systems are only maintained when there is problem. The few existing culvert are blocked

and natural drains unclear, full of sand. However, the best type of maintenance for the

drainage system is routine maintenance.

2.10 Culverts

The term “Culvert” is made up of practically all cleaned conduit used for highway drainage

and minor storm water drainage. Its main difference from bridge is that the top of the culvert

does not form part of travelled roadway. Culvert is to be found in three general locations.

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1- At the bottom of depressions where no natural water course exists.

2- Where natural streams or water courses intersect the roadway and,

3- At location needed for passing surface drainage carried inside ditches beneath roads

and driveways.

Majority of culvert are installed in natural water courses that cross the roadway, either at

right angles or on a skew. Beside a proper culvert location, the culvert crossing with respect

to the centerline of the road, the alignment and grade of the culvert are of importance. The

location of the centerline of the culvert on the centerline of the road may be determined by

inspection of plans or in the field. This location will generally be on the centerline of an

existing watercourse or all the bottom of depression. If no natural watercourse exists.

2.10.1 Types of culvert flow

A culvert placed in a stream channel will cause on abrupt change to the character of the

flow, chow V.T (1978). The culvert normally acts as a construction and the flow upstream is

slowed and ponds up above the culvert entrance. The flow within the culvert will have a free

surface if running partly full can either be subcritical or supercritical depending on the length

and gradient of the culvert and whether or not downstream levels are inducing backwater

effects. If the flow increases sufficiently, the entrance to the culvert will become drowned.

2.10.2 Culvert type and materials

Material most commonly used in the construction of culverts are reinforced concrete and

corrugated metal. Less frequently, culverts are made from timber, cast-iron pipe, vitrified-

clay pipe and occasionally stone masonry.

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2.10.3 Selection of culvert type

The type of culvert selected for a given location is dependent upon the hydraulic

requirements and the strength required to sustain the weight or of the material or moving

wheel loads. After those items have been established the selection is then largely a matter

of economic consideration which must be given to durability and to the cost of completed

structure.

2.11 Requirement of highway drainage system

1. The surface water from the carriage way and shoulder should effectively be drained

off without allowing it to percolate to sub-grade.

2. The surface water from the adjoining land should be prevented from entering the

roadway.

3. The surface drainage should have sufficient capacity and longitudinal slope to carry

away all the surface water collected.

4. Flow of surface water across the road and shoulders and along slopes should not

cause formation of erosion.

2.12 Design of surface drainage

- Hydrological analysis

- Hydraulic analysis

2.12.1 Hydrological analysis

This deals mainly with precipitation and runoff in the area of interest. When rainfall, which

is the main source of water, falls onto an area some of the water infiltrates into the soil while

the remaining portion either evaporates or runs off.

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The portion that remains as runoff is the one of major importance in the design of surface

drainage facilities.

2.12.2 Determination of runoff

Runoff at a particular point is determined with respect to a given catchment area and

depends on a number of factors such; type and condition of the soil in the catchment, kind

and extent of vegetation or cultivation, length and steepness of the slopes and the

developments on the area among others.

The following formula known as the rational formula is used for calculation of runoff water for

highway drainage,

𝑄 = 0.028𝐶𝐼𝐴 …………………………..I

Where:

𝑄 Is maximum runoff in m3 per sec

𝐶 Is a constant depending upon the nature of the surface

𝐼 Is the critical intensity of storm in mm per hour occurring during the time of

concentration.

𝐴 Is the catchment area in km2

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2.12.3 Hydraulic design

Once the design runoff Q is determined, the next thing to be done is hydraulic design of

drains. The side drainage and other structures are designed based on the principles of flow

through open channels.

If Q is the quantity of surface water (m3/sec) to be removed by a side drainage and V is

allowable velocity of flow (m/s) on the side drainage, the area of cross section A of the

channel (m2) is found from the relation below:

Q = A × V …………………………II

The velocity of unlined channel must be high enough to prevent silting and it should not be

too high as to cause erosion. The allowable velocity should be greater than (1m/sec) for

lined channel. Highway engineering manual vol.2

The slope S of the longitudinal drain of known or assumed cross section and depth of flow,

may determined by using Manning’s formula for the design value of velocity of flow V,

roughness coefficient n and hydraulic radius R.

Manning’s formula

V = 1

𝑛 × 𝑅2/3 × 𝑆1/2………………………..III

Where:

𝑉 = Average velocity m/sec

𝑛 = Manning’s roughness coefficient

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𝑅 = Hydraulic radius

𝑆 = Longitudinal slope of channel.

Manning’s roughness coefficient values,

CHANNEL MATERIAL PAVED MANNING’S n

GOOD – POOR

Vmax(m/s)

a. Concrete wall surfaces

i- Trowel finish

ii- Float finish

iii- Formed, no finish

0.012 – 0.014

0.013 – 0.015

0.014 – 0.015

6.1

6.1

6.1

b. Concrete bottom, float finished with

sides of:

i- Dressed stone in mortal

ii- Random stone in mortal

iii- Dressed stone or smooth concrete

rubble (rip-rap)

iv- Rubble or random stone ……. (rip-rap)

0. 015 – 0.017

0.017 – 0.020

0.02 – 0.025

0.035 – 0.030

5.5 – 6.1

5.2 – 5.8

4.6

4.6

c. Gravel bottom, side of:

i- Form

ii- Random stone in mortar

iii- Random stone or rubble (rip-rap)

0.017 – 0.020

0.020 – 0.023

0.023 – 0.033

3.0

2.4 – 3.0

2.4 – 3.0

d. Brick 0.014 – 0.017 3.0

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e. Asphalt 0.013 – 0.016 5.5 – 6.1

Highway engineering manual vol.2

Hydraulic Radius = 𝐶𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝑎𝑟𝑒𝑎

𝑊𝑒𝑡𝑡𝑒𝑑 𝑝𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟

2.12.4 Time of concentration (tc)

Time of concentration is that the time required for water to travel all the way from

catchment area to the designed element.

The time taken by water to flow along the longitudinal drain is determined from the length of

the longitudinal drain L the nearest cross drainage or a water course and allowable velocity

of the flow V in the drain.

𝑇 = 𝑉

𝐿 ……………………………IV

The total time for inlet flow and flow along the drain is taken as time of concentration or the

design value of rain fall duration.

tc = 𝑇1 + 𝑇2 …………………………..V

Where,

T1 is overland flow time in minutes

T2 is channel flow time in minutes

T1 = (0.885𝐿3

𝐻) 0.385 …………….……………...VI

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Where,

L = The length of overland flow in km from critical point to the mouth of the drain.

H = Total fall of level from the critical point to the mouth of the drain in meters.

Note:

From the rainfall intensity – duration – frequency curves the rainfall I is found in mm/sec.

corresponding to duration T and frequency of return period. Andrew L. S. (1976)

The required depth of flow in the drain is calculated for convenient bottom width and side

slope of drain. The actual depth of the open channel drain may be increased slightly to give

a free body. The hydraulic mean radius of flow R is determined.

The required longitudinal slope S of the drain is calculated using Manning formula adopting

suitable value of roughness coefficient.

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CHAPTER THREE

3.1 Drainage hydrology

This is the study of the movement, distribution and quantity of water in drainage system.

Therefore the hydrological design of drainage can be based on the rational formula as

recommended by “the highway manual part I”.

Here the runoff estimates is based on the rational method also known as the Lioyal Devies

method:

Empirically:

𝑄 = 0.278 𝐶𝐼𝐴 (m3/s) ……………………………I

Where:

𝑄 = Runoff from calculator (m3/hr)

𝐶 = Runoff coefficient expressed as a percentage of imperviousness of the

catchment surface.

𝐼 = Rainfall intensity of rate of rainfall corresponding to time of concentration (mm/hr).

𝐴 = Catchment area (km2)

The catchment area runoff Q, can be defined as the amount (quantity) of runoff expected

to be conveyed safely through designed drains. Results obtained using the above formula is

known to be precise for a particular area if direct data for the area is available.

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3.2 Estimating runoff coefficient C

A surface drainage system should be designed to handle the maximum rate of surface

runoff from rain to occur at urban area. The area, slope, vegetation and soil type must all be

considered.

For design of land drainage system, runoff coefficient is commonly assumed to be a

percentage of the rainfall.

For the purpose of estimating runoff coefficient C, the following percentages of rainfall are

assumed for the various surfaces below

Single house - - - - 60%

Garden apartments - - - 15%

Parks, farmland, pasture - - - 5%

Asphalt concrete pavement - - 20%

Total 100%

Source: Highway engineering manual vol.2

TABLE 3.1: Values of runoff coefficient C, for various surfaces

Value Value OFC

URBAN RESIDENTIAL: Single house, garden

apartments

0.3

0.5

COMMERCIAL AND INDUSTRIAL 0.9

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FORESTED AREA DEFENDING ON SOIL 0.05 – 0.20

PARKS, FARMLAND, PASURE 0.05 – 0.30

ASPHALT OR CONCRETE PAVEMENT 0.85 – 1.00

Source: Highway engineering manual vol.2

Therefore, C can be obtained by summing up the following;

Single house 0.6 × 0.3 = 0.18

Garden apartments 0.15 × 0.5 = 0.075

Farmlands 0.05 × 0.3 = 0.015

Asphalt concrete pavement 0.2 × 0.9 = 0.18

Total = 0.45

Therefore, coefficient of runoff (C) = 0.45

3.3 Rainfall intensity [I]

The time of concentration of a catchment area is the time required for water to flow down

the most remote part of the area to the outlet. There are a number of factors of flow that

influence the time of concentration. These include:

i- Time of overland flow (TOP)

ii- Time of channel flow (TCP)

Time of overland flow is influenced mainly by the ground slope, surface cover and flow

length. The time of concentration (tc), can be obtained empirically using

22

tc = 0.0197𝐿1.27

𝐻0.5 = ………………………………..VI

Where:

L = Length of watershed area (m)

H = difference in elevation between most remote point and outlet (m).

A maximum tc of 20 minutes is recommended for design except for inlets where a minimum

of 5 minutes should be used. (From “Practical Hydraulics” by Andrews L.S)

Therefore:

Tc of 5mins is taken which is approximately 0.08hr.

3.3.1 Rainfall Intensity [I]

This is the measure of the amount of rainfall per unit time. To obtain the rainfall intensity I,

parameters such as average frequency occurrence N, time of concentration tc, and rainfall

station constants a, b, A and B are used.

Rainfall intensity (I) = 𝐾𝑛

(𝑡𝑐+𝑎)𝑏 …………………………….II

Where:

Kn = (A + B) log n ……………………………III

The values for station constant for Kano are:

TABLE 3.2: Values for rainfall station constants

23

Constants

Stations A B A B

Lagos

Kano

Ikeja

0.333

0.500

0.600

0.861

1.032

0.952

2.18

2.95

3.28

1.44

1.91

2.34

Source: Highway manual Part 1

Using the station constant for Kano obtained from table 4.2

Kn = (2.95 + 1.91) log10 20 = 6.32

tc = 0.08hr.

From (ii),

Rainfall intensity (I) = 6.32

(0.08+0.5)1.032 = 11.08mm/hr ……………………….IV

3.4 Catchment area

The rational formula based on an assumption of complete rainfall coverage over a design

area. Though it’s the only element or the rational formula subject to accurate determination

of complete rainfall coverage, for large and extensive areas; two major considerations

require some modifications or the actual design area for the reasons:

1. The design rainfall should have a complete coverage over the design area.

24

2. Similarly the rainfall most occurs at a uniform intensity equal to the design intensity.

Calculation of catchment area

1. The satellite image of the area is obtained from the Google earth software

2. The catchment area is then marked out

3. The outlined was then plotted on the AutoCAD software.

4. The area was then measured from the AutoCAD area measuring tool.

Fig 3.1 Satellite image of the area obtained from Google earth

25

Fig 3.2 Plot of the area on AutoCAD

1. Area 1 was found to be 0.379 km2










26

3.5 Checking slopes at various locations using a profile leveling

Profile leveling is a method use to check the slope of drains at various location, the

equipment and procedure concerned are:

Equipments:

i- Dumpy level

ii- Tripod stand

iii- Tape

iv- Staffs

Procedure:

1) The instruments was set up at convenient location at the first station

2) The first station BM with assumed reduced level (RL) of 100m.

3) The staff was put erect at an interval of 30m each

4) A temporary bench mark (TBM) was established for change of position of

instrument and sighting was continued

5) The result was tabulated using the format below

Station BS IS FS HI RL Remarks

Where:

BS: Back sight

27

IS: Intermediate sight

FS: Fore sight

HI: Height of instrument, calculated after change of point by adding Bs and RL (Bs +

RL)

RL: Reduced level, calculated by subtracting 2nd value from 1st value, 3rd value from

2nd value …………........................... n – (n –1).

3.6 Determination of runoff

From the formula below;

𝑄 = 0.278𝐶𝐼𝐴

Where:

𝑄 = Quantity of rain water surface runoff in m3/sec

𝐶 = Surface runoff coefficient

𝐼 = Maximum rainfall intensity in mm/hour

𝐴 = Size of surface area to be drained in km2

𝐶 = 0.45

𝐼 = 11.08mm/hour

28

1. Determination of runoff for area 1

𝑄 = 0.278 × 0.45 × 11.08 × 0.379 = 0.525m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.77 = 1.07m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.822 = 1.14m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.98 = 1.36m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 1.31 = 1.82m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.379 = 0.525m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.77 = 1.07m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 0.822 = 1.14m3/s

29


𝑄 = 0.278 × 0.45 × 11.08 × 0.98 = 1.36m3/s


𝑄 = 0.278 × 0.45 × 11.08 × 1.31 = 1.82m3/s

3.7 Longitudinal slope and side slope

The longitudinal slope of the channel depends on the topography of the area. While the

side slope of the canal depends on the shape of the canal soil characteristic.

3.8 Canal dimensions

This involves determining the area and perimeter of the section and consists of depth of

flow (d) and width of channel (b). The dimensions are calculated from the equation of the

trapezoidal channel by assuming different values of flow, depth (d) using trial and error

procedure.

3.9 Freeboard (FB) and Top width (T)

Freeboard refers to the vertical distance between the highest water level in the proposed

design and the toe which is provided as a safety factor against over topping. While top width

is the total width of the section at the ground surface.

3.10 Design using SWMM software

The EPA storm water management model (SWMM) is a dynamic rainfall – runoff

simulation model used for single event or long – term (continuous) simulation of runoff

30

quantity and quality from primarily urban areas. The runoff component of SWMM operates

on a collection of subcatchment areas that receive precipitation and generate runoff and

pollutant loads. The routing portion of SWMM transports this runoff through a system of

pipes, channels, storage/ treatment devices, pumps and regulators. SWMM tracks the

quantity and quality of runoff generated within each subcatchment, and the flow rate, flow

depth, and quality of water in each pipe and channel during a simulation period comprised of

multiple time steps.

SWMM was first developed in 1971 and has undergone several major upgrades since

then. It continues to be widely used throughout the world for planning, analysis and design

related to storm water runoff, combined sewers, sanitary sewers and other drainage

systems in urban areas, with many applications in nonurban areas as well. The current

edition, Version 5.1, is a complete rewrite of the previous release. Running under Windows,

SWMM 5.1 provides an integrated environment for editing study area input data, running

hydrologic, hydraulic and water quality simulations, and viewing the results in a variety of

formats. These include color-coded drainage area and conveyance system maps, time

series graphs and tables, profile plots, and statistical frequency analyses.

This latest rewrite SWMM was produced by the Water Supply and Water Resources

Division of the U.S Environmental Protection Agency’s National Risk Management Research

Laboratory with assistance from the consulting firm of CDM, Inc.

SWMM conceptualizes a drainage system as a series of water and material flows

between several major environmental compartments. These compartments and the SWMM

objects they contain include:

31

The atmosphere compartment, from which precipitation falls and pollutants are deposited

onto the land surface compartment. SWMM uses Rain Gage objects to represent rainfall

inputs to the system.

The Land Surface compartment, which is represented through one or more subcatchment

objects. It receives precipitation from the Atmospheric compartment in the form of rain or

snow; it sends outflow in the form of infiltration to the Groundwater compartment and also as

surface runoff and pollutant loadings to be the transport compartment.

The Groundwater compartment receives infiltration from the land surface compartment and

transfers a portion of this inflow to the Transport compartment. This compartment is

modeled using Aquifer objects.

The Transport compartment contains a network of conveyance elements (channels, pipes,

pumps, and regulators) and storage/ treatment units that transport water to outfalls or to

treatment facilities. Inflows to this compartment can come from surface runoff, groundwater

interflow, sanitary dry weather flow, or from user-defined hydrographs. The components of

the Transport compartment are modeled with Node and Link objects.

Working with projects

Project files contain all of the information used to model a study area. They are usually

named with a.INP extension. This section describes how to create, open and save SWMM

projects and how to set their default properties.

Creating a new project

To create a new project:

32

Select File >> New

You will be prompted to save the existing project (if changes were made to it) before the

new project is created.

A new, unnamed project is created with all options set to their default values.

A new project is automatically created whenever SWMM first begins.

Open an existing project

To open an existing project stored on disk:

Select File >> Open

You will be prompted to save the current project (if changes were made to it).

Select the file to open from the Open File Dialog that appears.

Click Open to open the selected file.

To open a project that was worked on recently:

Select File >> Reopen

Select a file from the list of recently used files to open

Saving a project

To save a project under its current name either select File >> Save.

33

To save a project using different name, select File >> Save As. A standard Save File Dialog

will appear from which you can select the folder and name that the project should be saved

under.

Setting project defaults

Each project has to be set as default values that are used unless overridden by the SWMM

user. These values fall into three categories:

➢ Default ID labels (label used to identify nodes and links when they first created).

➢ Default sub catchment properties (e.g., area, width, slope, etc.)

➢ Default node/ link properties (e.g., node invert, conduit length, routing method)

To set default values for a project:

➢ Select Project >> Defaults

➢ A project defaults dialog will appear with three pages, one for each category listed

above.

➢ Check the box in the lower left of the dialog form if you want to save your choices for

use in all new future projects as well.

➢ Click Ok to accept your choice of defaults

Units of measurement

SWMM can use either US units or SI metric units. The choice of flow units determines what

unit system is used for all other quantities:

34

➢ Selecting CFS (cubic feet per second), GPM (gallons per minute) or MGD (million

gallons per day) for flow units implies that US units will be used throughout.

➢ Selecting CMS (cubic meters per second), LPS (liters per second) or MLD (million

liters per day) as flow units implies that SI units will be used throughout.

Flow units can be selected directly on the main window’s Status Bar or by setting a

project’s default values. In the letter case the selection can be saved so that all new future

projects will automatically use those units. The units of previously entered data are not

automatically adjusted if the unit system is changed.

Registering calibration data

SWMM can compare the results of a simulation with measured field data in its Time

Series Plots. Before SWMM can use such calibration data they must be entered into a

specially formatted text file and be registered with the project.

To register calibration data residing in a calibration File:

➢ Select Project >> Calibration Data

➢ In the calibration Data dialog that appears, click the box next to the parameter (e.g.,

node depth, link flow, etc.) whose calibration data will be registered.

➢ Either type in the name of a Calibration File for this parameter or click the Browse

button to search for it.

➢ Click the Edit button if you want to open the Calibration File in Windows Notepad for

editing.

➢ Repeat steps 2 - 4 for any other parameters that have calibration data

35

➢ Click Ok to accept your selections

Viewing all project data

A listing of all project data (with the exception of map coordinates) can be viewed in a

non-editable window, formatted for input to SWMM’s computational engine. This can be

useful for checking data consistency and to make sure that no key components are missing.

To view such a listing, select Project >> Details. The format of the data in this listing is the

same as that used when the file is saved to disk.

Working with objects

SWMM uses various types of objects to model a drainage area and its conveyance system.

This section describes how these objects can be created, selected, edited, and repositioned.

Types of objects

SWMM contains both physical objects that can appear on its Study Area Map, and

nonphysical objects that encompass design, loading, and operational information. These

objects, which are listed in the Projects Browser, consist of the following:

Project Title/ Notes Nodes

Simulation Options Links

Climatology Transects

Rain Gages Control Rules

Subcatchments Pollutants

36

Aquifers Land Uses

Snow Packs Curves

Unit Hydrographs Time Series

Unit Hydrographs Time Patterns

Lid Controls Map Labels

Adding an object

To add a new object to project, select the type of object from the upper pane of the Project

Browser and either select Project >> Add a New … from the Main Menu.

If the object is a visual object that appears on the Study Area Map (a Rain Gage,

Subcatchment, Node, Link or Map Label) it will automatically receive a default ID name and

a prompt will appear in the Status Bar telling you how to proceed. The steps used to draw

each of these objects on the map are detailed below:

Rain gages

Move the mouse to the desired location on the map and left-click.

Sub-catchment

Use the mouse to draw a polygon outline of the sub-catchment on the map.

➢ Left – click at each vertex

➢ Left – click at each vertex

37

➢ Right – click or press <Enter> to close the polygon

➢ Press the <Esc> key if you wish to cancel the action

Nodes

(Junctions, Outfalls, Flow Dividers and Storage Units)

Move the mouse to the desired location on the study area map and left – click.

Links

(Conduits, Pumps, Orifices, Weirs and Outlets)

➢ Left – click the mouse on the link’s inlet (upstream) node

➢ Move the mouse (without pressing any button) in the direction of the link’s outlet

(downstream) node, clicking at all intermediate points necessary to define the link’s

alignment.

➢ Left – click the mouse a final time over the link’s outlet (downstream) node. (Pressing

the right mouse button or the <Esc> key while drawing a link will cancel the

operation.)

Map labels

➢ Left – click the mouse on the map location where the top left corner of the label

should appear.

➢ Enter the text for the label.

➢ Press <Enter> to accept the label or <Esc> to cancel.

38

For all other non-visual types of objects, an object-specific dialog form will appear that

allows you to name the object and edit its properties.

Selecting an object

To select an object on the Study Area Map:

➢ Make sure that the map is in selection mode (the mouse cursor has the shape of an

arrow pointing up to the left). To switch to this mode, click Edit >> Select object from

the Main Menu.

➢ Click the mouse over the desired object on the map.

To select an object using the project browser:

➢ Select the object’s category from the upper list in the browser.

➢ Select the object from the lower list in the browser

Moving and object

Rain gages, subcatcments, nodes and map labels can be moved to another location on the

study area map. To move an object to another location:

➢ Select the object on the map.

➢ With the left mouse button held down over the object, drag it to its new location.

➢ Release the mouse button.

The following alternative method can also be used:

39

➢ Select the object to be moved from the Project Browse (it must be a rain gage,

subcatchment, node or map label).

➢ With the left mouse button held down, drag the item from the items list box of the

project browser to its new location on the map.

➢ Release the mouse button.

Note that the second method can be used to place objects on the map that were imported

from a project file that had no coordinate information included in it.

Editing an object

To edit an object appearing on the study area map:

➢ Select the object on the map.

➢ If the property editor is not visible either:

• Double click on the object.

• Menu that appears

• Select Edit >> Edit object from the Main Menu

➢ Edit the object’s properties in the Property Editor.

To edit an object listed in the Project Browser:

➢ Select the object in the Project Browser.

➢ Either:

• Select Edit >> Edit object from the Main Menu,

• Or double-click the item in Objects list,

• Or press the <Enter> key.

40

Depending on the class of object selected, a special property editor will appear in which the

object’s properties can be modified.

The unit system in which object properties are expressed depends on the choice of units for

flow rate. Using a flow rate expressed in cubic feet, gallons or acre-feet implies US units will

be used for all quantities. Using a flow rate expressed in liters or cubic meters means that SI

metric units will be used. Flow units are selected either from project’s default Node/Link

properties (see Setting Project Defaults) or directly from the main Window’s Status Bar.

Converting an object

It’s possible to convert a node or link from one type to another without having to first delete

the object and add a new one in its place. An example would be converting a Junction node

into an Outfall node, or converting an Orifice link into a Weir link.

To convert a node or link to another type:

➢ Right click the object on the study area map.

➢ Select Convert To from the popup menu that appears.

➢ Select the new type of node or link to convert to from the submenu that appears.

➢ Edit the object to provide any data that was not included with the previous type of

object.

Only data that is common to both types of objects will be preserved after an object is

converted to a different type. For nodes this includes its name, position, description, tag,

external inflows, treatment functions and invert elevation. For links it includes just its name,

end nodes, description and tag.

41

Copying and pasting objects

The properties of an object displayed on the Study Area Map can be copied and pasted into

another object from the same category.

To copy the properties of an object to SWMM’s internal clipboard:

➢ Right – click the object on the map.

➢ Select Copy from the pop-up menu that appears.

To paste copied properties into an object:

➢ Right – click the object on the map.

➢ Select Paste from the pop-up menu that appears.

Only data that can be shared between objects of the same type can be copied and pasted.

Properties not copied include the object’s name, coordinates, end nodes (for links), tag

property and any descriptive comment associated with object. For Map Labels, only font

properties are copied and pasted.

Deleting an object

To delete an object:

➢ Select the object on the Study Area Map or from the Project Browser.

➢ Press the <Delete> key on the keyboard, or select Edit >> Delete object from the

Main Menu, or right-click the object on the map and select Delete for the pop-up

menu that appears.

42

You can require that all deletions be confirmed before they take effect. See the

General References page of the Program Preferences dialog box.

Shaping a link

Links can be drawn as polylines containing any number of straight-line segments that define

the alignment or curvature of the link. Once a link has been drawn on the Study Area Map,

interior points that define these line segments can be added, deleted and moved.

To edit the interior points of a link:

➢ Select the link to edit on the Map in Vertex Selection mode by either by

• Selecting Edit >> Select Vertex from the Main Menu,

• Or right-clicking on the link and selecting Vertices from the popup menu.

➢ The mouse pointer will change shape to an arrow tip, and any existing vertex points

on the link will be displayed as small open squares. The currently selected vertex will

be displayed as a filled square. To select a particular vertex, click the mouse over it.

➢ To add a new vertex to the link, right-click the mouse and select Add Vertex from

the popup menu (or simply press the <Insert> key on the keyboard).

➢ To delete the currently selected vertex, right click the mouse and select Delete

Vertex from the popup menu (or simply press the <Delete> key on the keyboard).

➢ To move a vertex to another location, drag it with the left mouse button held down to

its new position.

➢ While in Vertex Selection mode you can begin editing the vertices for another link by

simply clicking on the link. To leave Vertex Selection mode, right-click on the map

43

and select Quite Editing from the popup menu, or simply select one of the other

buttons on the Map Toolbar.

A link can also have its direction reversed (i.e., its end nodes switched) by right clicking on it

and selecting Reverse from the popup menu that appears. Normally, links should be

oriented so that the upstream end is at a higher elevation than the downstream end.

Shaping a subcatchment

Sub-catchments are drawn on the Study Area Map as closed polygons. To edit or add

vertices to the polygon, follow the same procedures used for links (see Shaping a Link). If

the sub-catchment is originally drawn or is edited to have two or less vertices, then only its

centroid symbol will be displayed on the map.

Selecting a group of objects

A group of objects within an irregular region of the Study Area Map can have a common

property edited or be deleted all together. To select such a group of objects:

➢ Choose Edit >> Select region from the Main Menu.

➢ Draw a polygon around the region of interest on the Map by clicking the left mouse

button at each successive vertex of the polygon.

➢ Close the polygon by clicking the right button or by pressing the <Enter> key; cancel

the selection by pressing the <Esc> key.

To select all objects in the project, whether in view or not,

Select Edit >> Select All from the Main Menu.

44

Deleting a group of objects

To delete the objects located within a selected area of the Study Area Map (see selecting a

Group of Objects), select Edit >> Group Delete from the Main Menu. Then select the

categories of objects you wish to delete from the dialog box that appears. As an option, you

can specify that only objects with a specific Tag property should be deleted. Keep in mind

that deleting a node will also delete any links connected to the node.

Editing a group of objects

Once a group of objects has been selected (see Selection a Group of Objects), you can edit

a common property shared among them:

➢ Select Edit >> Group Edit from the Main Menu.

➢ Use the Group Editor dialog that appears to select a property and specify its new

value.

Working with the map

EPA SWMM can display a map of the study area being modeled. This section describes

how you can manipulate this map to enhance your visualization of the system.

Selection a map theme

A map theme displays object properties in color-coded fashion on the Study Area Map. The

dropdown list boxes on the Map Browser are used for selecting a theme to display for

Subcatchments, Nodes and Links.

Methods for changing the color-coding associated with a theme are discussed

45

Setting the map dimensions

The physical dimensions of the map can be defined so that map coordinates can be

properly scaled to the computer’s video display.

To set the map’s dimensions:

➢ Select View >> Dimensions from the Main Menu.

➢ Enter coordinates for the lower-left and upper-right corners of the map into the Map

Dimensions dialog that appears or click the Auto-size button to automatically set the

dimensions based on the coordinates of the objects currently included in the map.

➢ Select the distance units to use for these coordinates.

➢ If the Auto-Length option is in effect, check the “Re-compute all lengths and areas”

box if you would like SWMM to re-calculate all conduit lengths and sub-catchment

areas under the new set of map dimensions

➢ Click the Ok button to resize the map.

Running a simulation

After a study area has been suitably described, its runoff, routing and water quality behavior

can be simulated. This section describes how to specify options to be used in the analysis,

how to run the simulation and how to troubleshoot common problems that may occur.

Setting simulation options

SWMM has a number of options that control how the simulation of a storm water drainage

system is carried out. To set these options:

46

➢ Select the Options category from the Project Browser.

➢ Select one of the following categories of options to edit.

Viewing simulation results

This section describes the different ways in which the results of a simulation can be viewed.

These include a status report, a summary report, various map views, graphs, tables and a

statistical frequency report.

Viewing a status report

A Status Report is available for viewing after each simulation. It contains information on the

following

Analysis options

Input summary (if requested in the Simulation Options)

Rain File Summary

Error Messages

Control Action (if requested in the Simulation Options)

Continuity Errors

Stability Results.

To view the status report select Report >> Status from the Main Menu or click the button

and select Status Report from the drop-down menu that appears.

47

To copy selected text from the Status Report to a file or to the Windows Clipboard, first

select the text to copy with the mouse and then Select Edit >> Copy To from the Main

Menu.

To save both the entire Status Report and Summary Report to file, Select File >> Export >>

Status/ Summary Report from the Main Menu.

48

CHAPTER FOUR

Presentation of Result

4.1 Design of side drainage and discussion

4.1.1 Calculation of top width for conduits 1,2,3,6,7,8 using SWMM software.

Consider a trapezoidal section is shown in fig 4 below

The top widths of the drainage are calculated as shown below after obtaining the depths and

bottom widths from the software.

Fig 4.1 Typical trapezoidal section

Where,

B = Bottom width of section

49

y = Depth of section

d = Width of slanting side

tan ∅ =1

2= 0.5 ∅ = 26.57

tan ∅ = 𝑑

1

d = 1 × tan 26.57 = 0.5

top width = bottom width + 2d

= 0.5 + (2 × 0.5) = 1.5m

4.1.2 Calculation of top width for conduits 4,5,9 and 10.

Top width = bottom width + 2d

Top width = 1 + (2 × 0.5) = 2m

Table 4.1Dimension of the drainage obtained from the software

Conduit name Depth (m) Bottom width (m) Top width (m)

Conduit 1 1 0.5 0.5 + 0.5 + 0.5 = 1.5

Conduit 2 1 0.5 0.5 + 0.5 + 0.5 = 1.5

Conduit 3 1 0.5 0.5 + 0.5 + 0.5 = 1.5

Conduit 4 1 1 0.5 + 0.5 + 1.0 = 2.0

Conduit 5 1 1 0.5 + 0.5 + 1.0 = 2.0

Conduit 6 1 0.5 0.5 + 0.5 + 0.5 = 1.5

Conduit 7 1 0.5 0.5 + 0.5 + 0.5 = 1.5

50

Conduit 8 1 0.5 0.5 + 0.5 + 0.5 = 1.5

Conduit 9 1 1 0.5 + 0.5 + 1.0 = 2.0

Conduit 10 1 1 0.5 + 0.5 + 1.0 = 2.0

Fig 4.2 SWMM screen showing the map of the area

Calculations using manual design

4.2 Manual design

Trapezoidal section

Cross section area (A) of the side drainage required will be obtained from the continuity

equation;

Q = A × V ……………………………I

Where;

51

Q = Quantity of rain water surface runoff in m3/sec

A = Cross section area in m2

V = Velocity of flow in m/sec

Fig 4.12 Typical trapezoidal section

Area = (2 × area of ABE) + (area of bcef)

tan ∅ = 0.5

1 = 0.5

b = D tan 26.57 = 0.5D

Area of ABE = 0.5 × base × height

= 0.5 × 0.5D × D

52

Total area = (2 × 0.5 × 0.5D × D) + BD

= BD + 0.5D2

4.2.1 Design of conduits

Design of conduit 1 and 6

Q = 0.278 × 0.45 × 11.08 × 0.379 = 0.525m3/s

Q = A × V from (I)

A = 𝑄

𝑉=

0.515

1.5 = 0.35

Assume D = 0.7m

BD + 0.5D2 = 0.35m

0.7B + 0.5 × 0.72 = 0.35

B = 0.15m

b = 0.5D = 0.5 × 0.7 = 0.35m

Top width = 2b + B = (0.35 × 2) + 0.15 = 0.85m

Assume a free board of 0.15m

D = 0.85m

53

Fig 4.13 Required section for conduits 1 and 6

Longitudinal slope

From Manning’s

𝑉 = 2

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = ( 𝑣 × 𝑛

𝑅2/3 )2

Where,

R = hydraulic radius

R = 𝐶𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛 𝑎𝑟𝑒𝑎


For conduits 1 and 6

54

Cross sectional area = 0.35m2

Wetted perimeter is equal to the total length of the wetted area.

= Length of two side slope + Bottom length

Where;

Bottom length = 0.15m

Length of side slope is calculated below

From Pythagoras theorem,

x = (0.352 + 0.72)1/2

x = 0.783m

Wetted perimeter = 0.783 + 0.783 + 0.15

= 1.72m

55

𝑅 = 0.35

1.72= 0.203

𝑉 = 1

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = (1.5 × 0.025

0.2032/3 )2

𝑆 = 0.012

Design of conduits 2 and 7

Q = 0.278 × 0.45 × 11.08 × 0.77 = 1.07𝑚3/𝑆

Q = AV from (I)

𝐴 = 𝑄

𝑉=

1.07

1.5= 0.713𝑚2

Assume D = 0.75m

BD + 0.5D2 = 0.713

0.7B + 0.5 × 0.752 = 0.713

B = 0.51m

b = 0.5D = 0.5 × 0.75 = 0.375m

Top width = 2b + B = (0.375 × 2) + 0.51 = 1.25m

Assume a free board of 0.15m

D = 0.9m

56

Fig 4.14 required section for conduits 2 and 7

Longitudinal slope

For conduit 2 and 7

Cross sectional area = 0.713m2



Where;

Bottom length = 0.5m


57


x = (0.3752 + 0.752)2/1

x = 0.839m


= 2.19m

𝑅 = (0.713

2.19) = 0.326

𝑉 = 1

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = (1.5 × 0.025

0.3262/3)2

𝑆 = 0.0063

58


𝑄 = 0.278 × 0.45 × 11.08 × 0.822 = 1.14𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.14

1.5= 0.7582

Assume D = 0.75m

𝐵𝐷 + 0.5𝐷2 = 0.758

0.7𝐵 + 0.5 × 0.752 = 0.758

𝐵 = 0.605𝑚

𝑏 = 0.5𝐷 = 0.5 × 0.75 = 0.375𝑚

Top width = 2𝑏 + 𝐵 = (0.375 × 2) + 0.6 = 1.3𝑚

Assume a free board of 0.15𝑚

𝐷 = 0.85𝑚

59


Longitudinal slope

For conduit 3 and 8

Cross sectional area = 0.758𝑚2



Where;

Bottom length = 0.6𝑚

60



x = (0.3752 + 0.752)2/1

x = 0.839m


=2.28𝑚

𝑅 = (0.758

2.28) = 0.332

𝑉 = 1

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = (1.5 × 0.025

0.3322/3 )2

𝑆 = 0.00612

61


𝑄 = 0.278 × 0.45 × 11.08 × 0.98 = 1.36𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.36

1.5= 0.91𝑚2

Assume D = 1m

𝐵𝐷 + 0.5𝐷2 = 0.01

0.7𝐵 + 0.5 × 12 = 0.91

𝐵 = 0.41𝑚

𝑏 = 0.5𝐷 = 0.5 × 1 = 0.5𝑚

Top width = 2𝑏 + 𝐵 = (0.5 × 2) + 0.41 = 1.41𝑚, use 1.5𝑚


𝐷 = 1.15𝑚

62


Longitudinal slope

For conduit 4 and 9




Where;


63



x = (0. 52 + 1.02)2/1

x = 1.12m


=2.646𝑚

𝑅 = (0.91

2.646) = 0.344

𝑉 = 1

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = (1.5 × 0.025

0.3442/3)2

𝑆 = 0.00583

64


𝑄 = 0.278 × 0.45 × 11.08 × 1.31 = 1.82𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.82

1.5= 1.21𝑚2

Assume D = 1m

𝐵𝐷 + 0.5𝐷2 = 1.21

𝐵 + 0.5 × 12 = 1.21

𝐵 = 0.71𝑚

𝑏 = 0.5𝐷 = 0.5 × 1 = 0.5𝑚

Top width = 2𝑏 + 𝐵 = (0.5 × 2) + 0.71 = 1.71𝑚, use 1.8𝑚


𝐷 = 1.15𝑚

65


Longitudinal slope

For conduit 5 and 10




Where;



66


x = (0. 52 + 1.02)1/2

x = 1.12m


=2.95𝑚

𝑅 = (1.21

2.95) = 0.411

𝑉 = 1

𝑛 × 𝑅2/3 × 𝑆1/2

𝑆 = (1.5 × 0.025

0.4112/3 )2

𝑆 = 0.0046

67

4.3 Design of rectangular section

Design using SWMM software

A rectangular section is now chosen and the following dimensions were obtained as

shown in table 4.2 below.

Table 4.2: Dimensions obtained from the software

Conduit Name Depth (m) Width (m)

Conduit 1 1 1.0

Conduit 2 1 1.2

Conduit 3 1 1.2

Conduit 4 1 1.3

Conduit 5 1 1.5

Conduit 6 1 1.0

Conduit 7 1 1.0

Conduit 8 1 1.2

Conduit 9 1 1.3

Conduit 10 1 1.5

68

4.3.1 Manual design method

Consider the rectangular section shown in fig 4.8 shown below;

Fig 4.18 Typical Rectangular section

Area = 𝐵 × 𝐷

Where:

𝐵 =Width

𝐷 =Depth


𝑄 = 0.278𝐾𝐼𝐴

𝑄 = 0.278 × 0.45 × 11.08 × 0.379 = 0.525𝑚3/𝑠

69

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

0.525

1.5= 0.35𝑚2

Assume 𝐷 = 0.7𝑚

𝐵 × 𝐷 = 0.35

0.7𝐵 = 0.35

𝐵 = 0.5𝑚


𝐷 = 0.85𝑚


70

Longitudinal slope

𝑆 = (𝑉×𝑛

𝑅2/3)2

Where;


𝑅 = 𝐶𝑟𝑜𝑠𝑠 𝑠𝑒𝑐𝑡𝑖𝑜𝑛 𝑎𝑟𝑒𝑎


𝑅 = 0.35

0.7+0.5+0.75

𝑅 = 0.184

𝑆 = (1.5 ×0.025

0.1842/3 )2

𝑆 = 0.0134


𝑄 = 0.278𝐾𝐼𝐴

𝑄 = 0.278 × 0.45 × 11.08 × 0.77 = 1.07𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.07

1.5= 0.713𝑚2


𝐵𝐷 = 0.713

71

0.75𝐵 = 0.713

𝐵 = 0.95𝑚


𝐷 = 0.9𝑚


Longitudinal slope

𝑆 = (𝑉×𝑛

𝑅2/3)2

Where;


72



𝑅 = 0.713

0.75+0.95+0.75

𝑅 = 0.291

𝑆 = (1.5 ×0.025

0.2912/3 )2

𝑆 = 0.0073


𝑄 = 0.278𝐾𝐼𝐴

𝑄 = 0.278 × 0.45 × 11.08 × 0.822 = 1.14𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.14

1.5= 0.758𝑚2


𝐵𝐷 = 0.758

0.75𝐵 = 0.713

𝐵 = 1.5𝑚


𝐷 = 0.9𝑚

73


Longitudinal slope

𝑆 = (𝑉×𝑛

𝑅2/3)2

Where;




𝑅 = 0.758

0.75+1.5+0.75

𝑅 = 0.25

74

𝑆 = (1.5 ×0.025

0.252/3 )2

𝑆 = 0.00893


𝑄 = 0.278𝐾𝐼𝐴

𝑄 = 0.278 × 0.45 × 11.08 × 0.98 = 1.36𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.36

1.5= 091𝑚2

Assume 𝐷 = 1𝑚

𝐵𝐷 = 0.91

1 × 𝐵 = 0.91

Use 𝐵 = 0.9𝑚


𝐷 = 1.15𝑚

75


Longitudinal slope

𝑆 = (𝑉×𝑛

𝑅2/3)2

Where;




𝑅 = 0.91

1.0+0.9+1.0

𝑅 = 0.314

76

𝑆 = (1.5 ×0.025

0.3142/3 )2

𝑆 = 0.0066


𝑄 = 0.278𝐾𝐼𝐴

𝑄 = 0.278 × 0.45 × 11.08 × 1.31 = 1.82𝑚3/𝑠

𝑄 = 𝐴𝑉

𝐴 = 𝑄

𝑉=

1.82

1.5= 1.21𝑚2

Assume 𝐷 = 1𝑚

𝐵𝐷 = 1.21

1 × 𝐵 = 1.21

𝐵 = 1.21𝑚

Use 𝐵 = 1.2𝑚


𝐷 = 1.15𝑚

77


Longitudinal slope

𝑆 = (𝑉×𝑛

𝑅2/3)2

Where;




𝑅 = 1.21

1.0+1.2+1.0

𝑅 = 0.378

78

𝑆 = (1.5 ×0.025

0.3782/3 )2

𝑆 = 0.0051

4.4 Discussions

Both trapezoidal and rectangular sections are designed by the software and manual method

each. The results are summarized as shown in the tables below.

Trapezoidal section

Table 4.3: Comparison of depths obtained by software and manual design

Conduit Software depth (m) Manual depth (m)

Conduit 1 1.0 0.85

Conduit 2 1.0 0.90

Conduit 3 1.0 0.90

Conduit 4 1.0 0.15

Conduit 5 1.0 0.15

Conduit 6 1.0 0.85

Conduit 7 1.0 0.90

Conduit 8 1.0 0.90

Conduit 9 1.0 1.15

Conduit 10 1.0 1.15

From the above summary of results, it can be observed that the depths obtained by the

software are higher in conduits 1,2,3,6,7 and 8, while those obtained by manual design are

higher in conduits 4,5,9 and 10.

79

Therefore, the results (depths) given by the software should be used for conduits

1,2,3,6,7 and 8, while the depths obtained from manual design should be used for conduits

4,5,9 and 10, so as to have a safer hydraulic design.

Table 4.4: Comparison of bottom widths obtained by software and manual design

Conduit Software bottom width (m) Manual bottom width (m)

Conduit 1 0.5 0.15

Conduit 2 0.5 0.5

Conduit 3 0.5 0.6

Conduit 4 1 0.4

Conduit 5 1 0.7

Conduit 6 0.5 0.15

Conduit 7 0.5 0.5

Conduit 8 0.5 0.6

Conduit 9 1 0.4

Conduit 10 1 0.7

The bottom widths obtained from the software are higher in all conduits except 3 and 8.

Therefore, the results obtained from the software should be used for all conduits except 3

and 8 in which cases the bottom width obtained from the manual design should be used.

Table 4.5: Comparison of top widths obtained by software and manual design

Conduit Software bottom width (m) Manual bottom width (m)

Conduit 1 1.50 0.85

Conduit 2 1.50 1.25

Conduit 3 1.50 1.30

80

Conduit 4 2.00 1.50

Conduit 5 2.00 1.70

Conduit 6 1.50 0.85

Conduit 7 1.50 1.25

Conduit 8 1.50 1.30

Conduit 9 2.00 1.50

Conduit 10 2.00 1.70

The top widths obtained from the software are higher in all conduits; therefore the results

from the software should be used.

Rectangular section

Table 4.6: Comparison of depths obtained by software and manual design


Conduit 1 1. 0 0.85

Conduit 2 1. 0 0.90

Conduit 3 1. 0 0.90

Conduit 4 1. 0 1.15

Conduit 5 1. 0 1.15

Conduit 6 1. 0 0.85

Conduit 7 1. 0 0.90

Conduit 8 1. 0 0.90

Conduit 9 1. 0 1.15

Conduit 10 1. 0 1.15

From the above summary of results, it can be observed that the depths obtained by the

software are higher in conduits 1,2,3,6,7 and 8, while those obtained by manual design are

higher in conduits 4,5,9 and 10. Therefore, the results (depths) given by the software should

81

be used for conduits 1,2,3,6,7 and 8, while the depths obtained from manual design should

be used for conduits 4,5,9 and 10, so as to have a safer hydraulic design.

Table 4.7: Comparison of widths obtained by software and manual design


Conduit 1 1. 0 0.50

Conduit 2 1. 2 0.95

Conduit 3 1. 2 1.50

Conduit 4 1. 3 0.90

Conduit 5 1. 5 1.20

Conduit 6 1. 0 0.50

Conduit 7 1. 0 0.95

Conduit 8 1. 2 1.50

Conduit 9 1. 3 0.90

Conduit 10 1. 5 1.20

From the above summary of results, it can be observed that the results obtained from the

software are higher in all conduits except conduits 3 and 8. Therefore the results obtained

from the software should be used except in conduits 3 and 8 in which the results by manual

design should be used.

From the above summary of results obtained by both software and manual methods, it

can be observed that, by comparison, the dimensions are relatively slightly varied, with

higher figures obtained from the software for both trapezoidal and rectangular cross

sections. This is because the software is programmed to give safe hydraulic design.

Therefore the results obtained from the software are to used for this design.

82

Also the cross section of the trapezoidal section by both software and manual method will

contain more water that the rectangular section. Therefore as a result of the high discharge

in the area, the trapezoidal section obtained from the software should be used for this

design.

83

CHAPTER FIVE

Conclusion and Recommendation

5.1 Conclusion

Many problems were discovered on the road such as; flooding, potholes, overflow,

corrugations, water lodging, ruts, erosion on the edge of the road. However, as a result of

datas taken for the road and analysis carried out by inspection, practical checking of the

whole road and all areas surrounding the road, a roadside drainage was designed, and

therefore the above stated problems will be avoided when this design is implemented.

Hence in order to maintain the life span, purpose of the road, designing Roadside Drainage

of adequate size and capacity, the discharge and all dimensions produced can be used for

the construction as it is designed.

5.2 Recommendation

Due to the condition of the road is not satisfactory, this problem must be taken into

consideration by the use of the information gathered in this thesis. Therefore the road users

will be benefited by the design made in this thesis.

There will be need to performed routine maintenance for the constructed drainage in order

to avoid the blockage of the drains.

Also there should be subsequent projects on the assessment, and evaluation of the

performance of the drainage designed in this thesis.

84

However, the design will only be of maximum and lasting benefit when coupled with

adequate and durable structural design of the drainage. Structural design of the drainage is

therefore highly recommended.

85

Appendix I

Table 3.1: Values of runoff coefficient K, for various surfaces

Value Value of K

URBAN RESIDENTIAL: Single house, garden

apartments

0.3

0.5

COMMERCIAL AND INDUSTRIAL 0.9

FORESTED AREA DEFENDING ON SOIL 0.05 – 0.20

PARKS, FARM LAND, PASURE 0.05 – 0.30

ASPHALT OR CONCRETE PAVEMENT 0.85 – 1.00

Source: Highway Engineering manual vol. 2

86

Appendix II

Table 2.1:

Manning’s and maximum permissible velocity of flow in paved open channels

CHANNEL PAVED MANNING’S n

GOOD POOR

Vmax(m/s)

a. Concrete wall surfaces

i- Trowel finish

ii- Float finish

iii- Formed, no finish

0.012 – 0.014

0.013 – 0.015

0.014 – 0.015

6.1

6.1

6.1

b. Concrete bottom, float finished with

sides of:

i- Dressed stone in mortal

ii- Random stone in mortal

iii- Dressed stone or smooth concrete

rubble (rip-rap)

iv- Rubble or random stone ……. (rip-rap)

0. 015 – 0.017

0.017 – 0.020

0.02 – 0.025

0.035 – 0.030

5.5 – 6.1

5.2 – 5.8

4.6

4.6

c. Gravel bottom, side of:

i- Form

ii- Random stone in mortar

iii- Random stone or rubble (rip-rap)

0.017 – 0.020

0.020 – 0.023

0.023 – 0.033

3.0

2.4 – 3.0

2.4 – 3.0

d. Brick 0.014 – 0.017 3.0

e. Asphalt 0.013 – 0.016 5.5 – 6.1

Source: Highway Engineering manual vol. 2

87

Appendix III

Profile leveling for Kabuga to Tudunyola road using Height of Instrument Method

STATION B.S I.S F.S H.I R.L REMARK

0 + 030 1.08 101.08 100 TBM

0 + 060 1.83 99.25

0 + 090 1.54 99.54

0 + 120 0.60 0.50 101.18 101.58 C.P

0 + 150 1.27 99.91

0 + 180 0.90 100.28

0 + 210 1.20 99.98

0 + 240 1.30 99.88

0 + 270 1.25 1.15 101.28 100.03 C.P

0 + 300 1.61 99.67

0 + 330 1.85 99.43

0 + 360 1.98 99.30

0 + 390 2.15 99.13

0 + 420 1.76 99.52

0 + 450 1.49 1.52 101.25 99.76 C.P

0 + 480 1.27 99.98

0 + 510 0.73 100.52

0 + 540 0.58 100.62

0 + 570 0.14 101.11

0 + 600 0.36 100.89

0 + 630 0.25 101.00

0 + 660 0.09 101.16

0 + 690 0.30 100.95

0 + 720 0.47 100.78

0 + 750 0.10 101.15

0 + 780 1.50 1.60 101.15 99.65 C.P

0 + 810 1.06 100.09

0 + 840 1.15 100.00

0 + 870 0.75 100.40

0 + 900 0.27 0.16 101.26 100.99 C.P

0 + 930 0.65 100.07

0 + 960 0.2 100.51

0 + 990 0.48 1.20 100.54 100.06 C.P

1 + 020 99.86

1 + 050 100.34

88

1 + 080 1.40 1.03 100.91 99.51 C.P

1 + 110 1.07 99.84

1 + 140 0.49 100.42

1 + 170 1.62 99.29

1 + 200 0.90 1.47 100.34 99.44 C.P

1 + 230 1.20 99.14

1 + 260 1.47 99.87

1 + 290 1.32 99.02

1 + 320 1.38 98.96 C.P

89

References:

• Abiola. “Design of Storm Drainage” Magazine of storm drainage research, 2002, 54(1),

p. 7-12. (1985)

• Andrew L.S. “Practical Hydraulics”, John Willey &Sons. (1976)

• Chow V.T. “Open Channel Hydraulics”, International student edition, Megrawhill

International Book Company, U.S.A. (1978)

• Khanna P.N. “Practical Civil Engineers Handbook” New 9th edition, India, (1982)

• Sharma R.K, Sharma T.K. “Irrigation Engineering: Including Hydrology”, (2002)

Documents

Design of Roadside Drainage - Atlantic International University...iii Abstract This thesis work is concerned with the design of roadside drainage, in Kabuga to Tudunyola area of Kano