DESIGN OF AN OVERFLOW CONCRETE WEIR FOR UNIVERSITY OF

DESIGN OF AN OVERFLOW CONCRETE WEIR FOR

UNIVERSITY OF ILORIN SUGARCANE RESEARCH FIELDS

BY

ADEBAYO, LUKMAN

(08/30GB092)

JULY, 2012.

ii

DESIGN OF AN OVERFLOW CONCRETE WEIR FOR

UNIVERSITY OF ILORIN SUGARCANE RESEARCH FIELDS

BY

ADEBAYO, LUKMAN (08/30GB092)DEPARTMENT OF CIVIL ENGINEERING

UNIVERSITY OF ILORINILORIN, NIGERIA.

A PROJECT REPORT SUBMITTED TO THE DEPARTMENT OF CIVILENGINEERING, UNIVERSITY OF ILORIN, IN PARTIAL FULFILLMENT

OF THE REQUIREMENT FOR THE AWARD OF BACHELOR OFENGINEERING DEGREE IN CIVIL ENGINEERING

JULY, 2012.

iii

CERTIFICATION

This project has been read and approved as meeting the requirements of the

department of Civil Engineering, University of Ilorin, for the award of Bachelor

of Engineering (B. Eng) degree in Civil Engineering.

……………………........... …………………..Dr. O.G. Okeola DATESupervisor

……………………......... …………………..Dr. A.A. Jimoh DATEHead of Department

……………………............. ....…………………EXTERNAL EXAMINER DATE

iv

DEDICATION

This project is dedicated to Almighty Allah, the source of my inspiration. Also

to my parents and my boy, Abdulsamad Opeyemi for inspiring my dream.

v

ACKNOWLEDGMENT

I am grateful to Almighty God who saw me through my academic programme

in this noble institution. Also I acknowledge my parents and siblings for their

unconditional love and support.

My sincere appreciation goes to my esteem supervisor and able lecturer,

Dr. O.G. Okeola, for all the support he gave me throughout this project work. I

cannot mention them all but I just pray Almighty ALLAH continue to

replenished him in His infinite mercy. I am heartily thankful to everybody that

made my stay in this institution easy and contribute to my success today most

especially Mr Wahab Yunus for granting me access to his computer system.

Jazakumul-llah khaeran.

vi

ABSTRACT

The proposed overflow concrete weir for University of Ilorin sugarcane

research fields was intended to improve the water storage needed to

irrigate the farm and also to control the flood hazards at the downstream

communities. The Snyder and Soil Conservation Service (SCS) methods of

hydrograph analysis were used and the maximum 24-hr rainfall depth of

50yrs return period for the river Oyun catchment was estimated using the

Snyder method as 180.56m3/s.

The estimated peak flow was adopted for the design of the weir. The

length of the overflow weir is 30m, the total depth of the water above the

weir base on 50yrs returned period was estimated as 1.02m. This implies

that there is about 29% increase in the total depth of water above the

overflow weir. The determined height of the concrete weir and base width

were 2.5m and 2.0m respectively. The criteria for the weir stability were

also satisfied.

vii

TABLE OF CONTENT

Title page `i

Certification ii

Dedication iii

Acknoledgement iv

Abstract v

Table of content vi

List of tables ix

List of figures ix

CHAPTER ONE: Introduction

1.1 General information 1

1.2 Justification of the study 4

1.3 Scope of the project 4

1.4 Description of study area 5

CHAPTER TWO: Literature Review

2.1 General review 7

2.2 Theory of unit hydrograpy 8

2.2.1 Snyder method 8

2.2.2 Soil conservation service (SCS) method 9

2.2.3 Unit hydrograph derivation 9

2.3 Weir 10

2.3.1 Types of weir 10

2.3.1.1 Broad-crested weir 11

2.3.1.2 Sharp crested weir 11

2.3.1.3 Combination weir 11

viii

2.3.1.4 V-notch weir 12

2.3.1.5 Minimum energy loss weir 12

2.4 Civil engineering standard method of measurement 13

2.4.1 Preparation of bill of quantities 13

2.4.1.1 Preamble 14

2.4.1.2 Preliminaries 14

2.4.1.3 Coding and numbering 15

CHAPTER THREE: Methodology

3.1 Data collection 16

3.2 Calculation of unit hydrograph characteristics 18

3.2.1 Snyder method 18

3.2.1.1 Lag time 18

3.2.1.2 Basin lag time 18

3.2.1.3 Peak discharge 19

3.2.1.4 Peak discharge per unit area 20

3.2.1.5 Base time 21

3.2.1.6 Width estimation of unit hydrograph 21

3.2.2 Soil conservation service method 22

3.2.2.1 Convertion factors 24

3.2.3 Development of design storm hydrograph 25

3.3 Design of concrete weir

3.3.1 Water pressure on overflow section 29

3.3.2 Estimation of water pressure and overturning moment 31

3.3.3 Force due to selfweight and resisting moment 32

3.3.4 Stability analysis 33

3.3.5 Uplift force on the base of concrete weir 35

3.3.6 Uplift pressure in the body of the concrete weir 36

ix

3.3.7 Vertical stress on the concrete weir 37

3.3.8 Principal and Shearing stresses at the toe 37

3.4 Concrete volume 38

3.5 Preparation of bill of quantity 39

3.5.1 Quantity computation 39

CHAPTER FOUR: Results and Discussion

4.0 Results and Discussion 40

CHAPTER FIVE:Conclusion and Recommendation

5.1 Conclusion 41

5.2 Recommendation 41

References 42

x

LIST OF TABLES

Table Description Page

3.1 Watershed parameter for river Oyun 18

3.2 Synthetic unit hydrograph parameter for 10hrs storm duration 20

3.3 Storm hydrograph ordinate for Oyun watershed 26

3.4 Coordinates of the design hydrograph 28

3.5 Forces due to self-weight and resisting moment 33

3.6 Design parameter for the concrete weir from the analysis 38

3.7 Bill of engineering measurement and evaluation 39

xi

LIST OF FIGURES

Figure Description Page

1.1 Existing weir discharging water to the downstream side 6

1.2 Existing weir showing the water reservoir at the upstream side 6

3.1 Satellite imagery showing the location of the existing weir 17

3.2 A plot of 50-yr, 24-hr storm hydrograph 27

3.3 Hydrograph curve showing a plot of discharge againt time 29

3.4 Concrete weir section and pressure diagram 30

3.5 Concrete weir section divided into three sections 31

3.6 Uplift pressure diagram when there is water on the

downstream side 35

3.7 Uplift pressure diagram in the body of the concrete weir 36

xii

NOTATION

∅ Angle made by axial force to the vertical at the downstream

Storage coefficient

Storm duration

Overturning stability

Sliding stability

vertical stress on the concrete weir

Hydraulic height

Height of the concrete weir

Overturning moment

Resisting moment

Horizontal component of the force due to water pressure

Peak discharge

Base time

TIme to peak

Uplift pressure

Velocity head of water

Width estimation of 50% unit hydrograph

Width estimation of 75% unit hydrograph

Peak discharge per unit area

Bsin lag time

Time to recession

Top width of the weir

Base top width of the weir

Density of water

Principal stresses

xiii

Shearing stresses

A catchment area

Ct Coefficient representing variation of watershed

D Duration of excess rainfall

L river length

tL Length outlet to control

Base width

Runoff volume

Eccentricity

The value of each unit of time on the dimensionless hydrograph

Moment arm

The ratio of the total runoff volume to the area under dimenssionless

hydrograph

The ratio of the peak runoff for the design storm to peak flow of 100

units on the dimensionless hydrograph

Weight of the cocrete weir

Centroid

Point at which act from the toe of the weir

Design of an Overflow Concrete Weir for University of Ilorin Sugarcane Research Fields 2012

1

CHAPTER ONE

INTRODUCTION

1.1 General Introduction

Flood prediction is an essential tool in the design of dam, drainages, weirs,

culverts, and all other flood control structures. Thus flood prediction otherwise

known as the peak flow prediction refers to the process of transformation of

rainfall into a flood hydrograph and to the translation of that hydrograph

throughout a watershed or any other hydrologic system (Ramirez, 2000).

The theory of unit hydrograph was developed by Sherman and has been

subjected to modifications by a number of researchers, but the basic principles

have remained unchanged. The unit hydrograph (UH) of a drainage basin is

defined as the hydrograph of direct runoff resulting from 1cm of excess runoff

generated uniformly over the basin at a uniform rate from a storm with

specified durations (Salami, 2010). The duration of the unit volume of excess or

effective rainfall, sometimes referred to as the effective duration, defines and

labels the particular unit hydrograph. The unit volume is usually considered to

be associated with 1cm of effective rainfall distributed uniformly over the

basin area.

The study of unit hydrograph used covers basically two methods; the Snyder

and the soil conservation service (SCS). The ordinate of the unit hydrograph

was picked at 1hr interval and used to generate storm hydrographs from which

the peak flow of 50yr return period were determined for the design of

concrete weir. The volume of concrete required for the construction of the

weir was estimated and subsequently used to calculate the cost. The unit


2

hydrograph was adopted due to lack of hydrological data at the site. The

method of developing hydrograph without stream flow data are usually

affected by the watershed characteristics. These characteristics include the

area of the watershed, land slope, channel slope, channel length, soil type,

vegetation cover, land used and channel roughness. Each of these

characteristics plays a significant role in the resulting hydrograph for the

watershed.

Sule et al., (2011) recommend that the synthetic unit hydrograph development

method of storm hydrograph should not be used in catchments with an area

greater than 500 kilometer square, where the assumption of nearly uniform

net rainfall cannot be justified. Conversely, it may be argued that in large

catchments, the existence of spatial and temporal averaging coupled with the

dominance of channel routing, means a linear model (unit hydrograph) may be

highly appropriate.

It is therefore desirable to evaluate or examine and compare the storm

hydrograph model of Snyder and United states soil conservation service (SCS),

using river Oyun with catchment area of 573 kilometer square to explore the

most efficient model in the determination of design peak flow. There have

been many studies that relate hydrograph features to watershed

characteristics. A storm hydrograph is as a result of the complex effects of

rainstorm, watershed characteristics and soil moisture within the basin prior to

the storm.

Snyder developed empirical formula using the morphological characteristics of

the watershed. The United States soil conservation service (SCS) synthetic unit


3

hydrograph method was based on methods well established to overcome the

non-availability of data in an ungauged watershed. Hence the need for a

thorough comparison of the two methods since the outcome is of immense

benefits to man and his environment.

This studies aims at evaluating each of the two methods and comparing the

different hydrograph development to facilitate the design of an overflow

concrete weir. A concrete overflow weir is a solid structure, made of concrete

or masonry, constructed across a river to create a reservoir at its upstream

(Ahmad, 2004). The section of a concrete weir is approximately triangular in

shape, with its apex at the top and maximum width at the bottom. The section

is so proportioned that it resists the various forces acting on it by its own

weight. Early concrete weirs were built of masonry, but most of the modern

weirs were built of concrete.

Concrete weir is usually provided with overflow spillway in some portion of its

length. The weir thus consists of two sections namely; the non-overflow

section and the overflow section or spillway section. The design in this report is

for the overflow section. The weight of the dam is the main stabilizing force in

a gravity dam. For computation, the cross sectional area of the weir is divides

into simple shapes, triangle, rectangle, etc. where the area and centriod can

easily be calculated. Hence, weight components can be found.

Water pressure acts on the upstream i.e. the direction of the water current

(the upstream pressure is the main overturning force) and on the downstream

i.e. tail water pressure helps in the stability. The weir is under an uplift


4

pressure when water enters the pores, thereby creating cracks and fissures

within the weir body and acts in all directions.

1.2 Justification of the Study

In most watersheds in Nigeria, there is considerable lack of data with regard to

rainfall and river discharges. This study aims at evaluating different storm

hydrographs development methods by generating the peak flows at a

predicted return period to facilitate the design of weir across a tributary of

river Oyun as a case study.

1.3 Objectives of the Study

This project is aimed at the design of an overflow concrete weir for University

of Ilorin sugarcane research fields. The specific objectives of the study include:

1. To evaluate storm hydrograph on Oyun river basin using the Snyder and

soil conservation service (SCS) unit hydrograph methods.

2. To produce a satisfactory correlation between rainfall and runoff such

that rainfall excess runoff can be predicted.

3. To make comparison between peak flows obtained using the Snyder and

SCS methods based on different return periods.

4. To design an overflow weir base on predicted peak flow.

5. To give recommendation with respect to safety of the concrete weir in

the immediate community.

1.4 Scope of the Project

The procedure utilized in the hydrograph generation was limited to the

development of unit and storm hydrograph based on Snyder and SCS synthetic

unit hydrograph methods. It illustrates the accuracy and application of the


5

relations developed for the computation of synthetic unit hydrographs for

Oyun river basin. Comparison of discharges by the two methods for 50yrs

return periods and the design of overflow concrete weir using the peak

discharges estimated from the unit hydrograph ordinates obtained from

Snyder method.

1.5 Description of Study Area

The catchment of Oyun river lies within Kwara state. Its total area is 573km2,

the maximum length of this catchment is 48.30km and the average slope of the

area is 0.003%. The topography is a fair representative of surrounding plains

which can be described as undulating with very broad and gentle slopes

(Salami, 2010).

The weir is located downstream of the University of Ilorin dam. The stream

serves as the main source of water for University of Ilorin campus and also the

major source for irrigating the sugarcane fields. Figure 1.1 represents the study

location showing the existing weir discharging water to the downstream side

of the river while Figure 1.2 represents the water reservoir at the upstream

side of the existing weir.


6

Figure 1.1: The existing weir discharging water to the downstream side.

Figure 1.2: The existing weir showing the water reservoir at the upstream side.


7

CHAPTER TWO

LITERATURE REVIEW

2.1 General Review

The unit hydrograph is a method of estimating runoff. It was reported by

Ramirez (2000) that unit hydrograph was first proposed by Sherman in 1932

and since then it has been used as a key concept. The unit hydrograph is

defined as the watershed response to a unit depth of excess rainfall uniformly

distributed over the entire watershed and applied at a constant rate to a given

period of time.

A significant contribution to the unit hydrograph theory was given by Clark

1945 who proposed a unit hydrograph based on combination of a pure

translation routine process followed by a pure routine process. Although Clark

does not develop a spatial distributed analysis, the translation part of the

routine process is based on the time area diagram of the watershed. The

storage part consists of routine and response of the translation through a

linear reservoir located at the watershed outlet. The detention time of the

reservoir is selected in order to reproduce the falling limb of observed

hydrographs. Note that the actual traveling time of a water particle, according

to this approach is the travel time given by the time-area diagram plus the

detention time of the reservoir which is somewhat inconsistent.

Many components of the rainfall-runoff process in a catchment are difficult to

observe routinely and unambiguously as they require costly measuring

facilities. An important component of this process is the runoff volume whose


8

temporal variation needed to determine yield of a catchment besides use in

many hydrological applications such as bridges, dams, reservoirs etc.

Salami (2010) reported that Chow et al., (1988) discussed the derivation of unit

hydrograph and its linear system theory. Furthermore Viessman et al., (1989)

and Arora (2004) presented the history and procedure for several unit and

runoff hydrograph methods. Ogunlela and Kasali (2002) applied four methods

of unit hydrographs generation to develop unit hydrograph for an unguaged

watershed. The outcome of the study revealed that there are significantly

differences in these methods except for Snyder and SCS methods which were

not significantly different from each other. Salami et al., (2010) came out with

a report that the designed concrete overflow weir over river Wuruma will

improve water supply to Kiaima, headquarters of Kiaima LGA in Kwara state.

Some of the unit hydrograph authorities are Snyder (1938), Taylor and Schwarz

(1952), Soil conservation service SCS (1957), Gray (1961), Espey and Winslow

(1974) are available in hydrological literature (Ayanshola et al., 2009).

2.2 Theory of Unit Hydrograph

2.2.1 Snyder Method

The synthetic unit hydrograph of Snyder is based on relationships found

between three characteristics of a standard unit hydrograph and descriptors of

basin morphology (Ramirez, 2000). These relationships are based on a study of

20 watersheds located in the Appalachian Highlands and varying in size from

10 to 10,000 square miles. The hydrograph characteristics are the effective

rainfall duration, tr, the peak direct runoff rate qp, and the basin lag time tl and

from these relationships, five characteristics of a required unit hydrograph for

a given effective rainfall duration may be calculated. These characteristics


9

include the peak discharge per unit of watershed area, , the basin lag, tlr,

the base time, and the widths, (in time unit) of the unit hydrograph at 50

and 75 percent of the peak discharge.

2.2.2 Soil Conservation Service (SCS) Method

The dimensionless unit hydrograph developed by the soil conservation service

has been obtained from the UH’s for a greater number of watersheds of

different sizes and for many different locations. The SCS dimensionless

hydrograph is a synthetic UH in which the discharge is expressed as the ratio of

discharge, q, to peak discharge, qp and the time by the ratio of time, t, to time

to peak of the UH, tp. Given the peak discharge and the lag time for the

duration of the excess rainfall, the UH can be estimated from the synthetic

dimensionless hydrograph for the given basin (Suresh, 2005).

2.2.3 Unit Hydrograph Derivation

To derive the unit hydrograph from a simple rainstorm divide the direct

discharge values of time-discharge curve by the height of effective rainfall to

get the unit hydrograph. Suppose that there are M pulses of excess rainfall and

N pulses of direct runoff are observed in a storm. Then N-M+1 value will be

needed to define the unit hydrograph. The discrete convolution equation,

given below allows the computation of direct runoff Qn given excess rainfall Pm

and the unit hydrograph Un-m+1.The reverse process is called deconvolution

(Uditha, 2011).

Mn

1m1mnmn UPQ (2.1)


10

2.3 Weir

A weir is a small overflow dam used to alter the flow characteristics of a river or

stream (Wikipedia, 2011). In most cases weirs take the form of a barrier across the

river that causes water to pool behind the structure (not unlike a dam), but allows

water to flow over the top. Weirs are commonly used to alter the flow regime of

the river, prevent flooding, measure discharge and to help render a river

navigable. Some old world famous weirs includes the weir on the Humber River

near Raymore park in Ontario, Toronto, the weir at the Thorp grist mill in Thorp,

Washington, the weir in Warkworth, New Zealand (Wikipedia, 2011).

Weirs allow hydrologist and engineers a simple method of measuring the

volumetric flow rate in small to medium-sized streams, or in industrial

discharge locations. Since the geometry of the top of the weir is known, and all

water flows over the weir, the depth of water behind the weir can be

converted to a rate of flow. The calculation relies on the fact that fluid will pass

through the critical depth of the flow regime in the vicinity of the crest of the

weir. If water is not carried away from the weir, it can make flow measurement

complicated or even impossible. A weir may be used to maintain the vertical

profile of a stream or channel, and is then commonly referred to as a grade

stabilizer such as the weir in Duffield, Derbyshire (Wikipedia, 2011).

2.3.1 Types of Weir

There are different types of weir. It may be a simple metal plate with a V-notchcut into it or it may be a concrete and steel structure across the bed of a river.A weir that causes a large change of water level behind it as compared to theerror inherent in the depth measurement method will give an accurateindication of the flow rate. Some weirs are used as bridges for people to walkalong.


11

2.3.1.1 Broad-crested weir

A broad-crested weir is a flat-crested structure with a long crest compared to

the flow thickness (Sturm 2001; Chanson 2004). When the crest is broad, the

streamlines become parallel to the crest invert and the pressure distribution

above the crest is hydrostatic. The hydraulic characteristics of broad-crested

weirs were studied during the 19th and 20th centuries. Practical experience

showed that the weir overflow is affected by the upstream flow conditions and

the weir.

2.3.1.2 Sharp crested weir

A sharp-crested weir allows the water to fall freely away from the weir. Sharp

crested weirs are typically 1/4" or thinner metal plates. Sharp crested weirs

come in many different shapes such as rectangular, V-notch and Cipolletti

weirs (Wikipedia, 2011).

2.3.1.3 Combination weir

The sharp crested weirs can be grouped into three groups according to the

geometry of weir: (a) the rectangular (b) the V or triangular notch and (c)

special notches, such as trapezoidal, circular or parabolic. For accurate flow

measurement over a wider range of flow rates, a combine V-notch with a

rectangular weir can be employed.


12

2.3.1.4 V-notch weir

The V-notch weir is a triangular channel section used to measure small

discharge values. The upper edge of the section is always above the water level

and so the channel is always triangular simplifying calculation of the cross-

sectional area. V-notch weirs are preferred for low discharges as the head

above the weir crest is more sensitive to changes in flow compared to

rectangular weirs.

2.3.1.5 Minimum energy loss weir

The concept of the Minimum Energy Loss (MEL) structure was developed by

Gordon McKay in 1971. The first MEL structure was the Redcliff storm

waterway system, also called Humpy bong Creek drainage outfall, completed

in 1960 in the Redcliff peninsula in Australia (Wikipedia, 2011). It consisted of

MEL weir acting as a streamlined drop inlet followed by a 137 m long culvert

discharging into the Pacific Ocean. The weir was designed to prevent beach

sand being washed in and choking the culvert as well as to prevent salt

intrusion in Humpy bong Creek without a flux. The structure is still in use and

passed floods greater than the design flow in several instances without

flooding (Chanson, 2004).

The concept of the Minimum Energy Loss (MEL) weir was developed to pass

large floods with minimum energy loss and afflux, and nearly-constant total

head along the waterway. The flow in the approach channel is contracted

through a streamlined chute and the channel width is minimum at the chute


13

toe, just before impinging into the downstream natural channel. The inlet and

chute are streamlined to avoid significant form losses and the flow may be

critical from the inlet lip to the chute toe at design flow. MEL weirs were

designed specifically for situations where the river catchment is characterized

by torrential rain falls and by very small bed slope.

2.4 Civil Engineering Standard Method of Measurement (CESMM)

The main purpose of the Bill of Quantities is to assist the contractors to

produce an accurate tender figure efficiently and to enable post contract

administration in carried out an efficient and cost-effective manner. Estimation

is the process of pricing based on the available information, specification, and

various drawings toward arriving at total sum known as tender sum. This is to

be done within the context of form of contract and terms in which the sum will

apply (Okeola, 2012). Cost index is a tool used for project estimation and even

cost control for this reason correct application must be made to suit individual

and locality situations

2.4.1 Preparation of Bill of Quantities

Bill of Quantities is more appropriate to a building contract where the general

summary contains a list of individual Bills. In civil engineering documents the

equivalent Bills are called Parts so the overall document is a Bill of Quantities.

The pre-contract exercise of measuring the work also applies to the post-

contract task of measurement. The correct term for this task is re-

measurement where the work is physically measured on site or

admeasurement where the actual quantities are calculated from records.


14

There are five sections in the Bill of Quantities. These sections include:

1. Preamble

2. List of Principal Quantities

3. Day work Schedule

4. Work Items (divided into parts)

5. Grand Summary

2.4.1.1 Preamble

The Preamble is an extremely important section of the Bill of Quantities and is

the potentially vital source of information to the estimator. If any other

Methods of Measurement have been used in the preparation of the Bill of

Quantities, the fact should be recorded there (Okeola, 2012). For this study the

material cost such as cost of concrete per meter cube was sourced from the

chief quantity surveyor of the University of Ilorin, physical planning unit. Also

some other cost such as the cost of demolition of the existing weir was

sampled from some artisans in Tanke tipper garage.

2.4.1.2 Preliminaries

The preliminaries section of the bill of quantities is the engineer or QS’s

introduction to the contract. The section provides information on the location,

size, and complexity of the project and gives details of the conditions of

contract under which the project is to be implemented (Okeola, 2012). This

aspect is of huge important to this study considering the complexity of the

work and the proximity to the area. In this view, the cost in the preliminaries

cover mobilization of workers and equipment, channelization of the river,

provision of access route to the area e.t.c.


15

2.4.1.3 Coding and numbering

The aim of the coding is to produce a uniformity of presentation to assist the

needs of the estimator and the post-contract administration. There is a typical

presentation of coding and numbering of estimated items in the bill of

engineering measurement and evaluation (BEME) of this report (Table 3.7).


16

CHAPTER THREE

METHODOLOGY

3.1 Data Collection

The catchment of river Oyun is located between latitude 90 50’ and 80 24’ North

and longitude 40 38’ and 40 03’ East (Ayanshola et al., 2009). Oyun river lies

entirely within Kwara state of Nigeria and the river flow across University of

Ilorin campus. The project site is downstream of University of Ilorin dam.

River Oyun covers a catchment area of 573 km2 and the length of the river is

48.30 km to the weir axis. The method employed in the collection of the data

involves the collection of the topographical map covering the project site.

Figure 3.1 shows the satellite imagery of the case study. The catchment area,

the river length, the length along the main stream to a point nearest to the

basin centroid, catchment slope and the channel slope were obtained from

Sule et al., (2011).

Snyder and the soil conservation services (SCS) methods were used to generate

the peak discharge and the storm hydrograph of 50yrs return period were

determined. The peak flows obtained were subsequently used in the design of

the concrete weir. The watershed characteristics of the river are presented in

Table 3.1


17

Figure 3.1: Satellite imagery showing the location of the existing weir.


18

Table 3.1 Watershed parameters for River Oyun.

A L Lc Ct Cp TL D Sc(km2) (km) (km) (hr) (hr)

573 48.30 27.87 1.60 0.6 10.00 1.82 0.003Source: Sule et al.,(2011).

3.2 Calculation of Unit Hydrograph (UH) Characteristics

Catchments area A =573 km2

River Length L = 48.30 km

Length (outlet to control) Lc=27.86km

3.2.1 Snyder Method

3.2.1.1 Lag time tL

tL = Ct (L x Lc)0.3 (3.1)

Ct is a coefficient representing variation of watershed slope and storage which

ranges from 1.0 to 2.2 (Arora, 2004). An average value of 1.60 was assumed

the best for the catchment.

tL= 1.6(48.30 × 27.86)0.3= 9.998≅ 103.2.1.2 Basin lag time

Adjusted basin lag time for 1hr storm duration is given ast = t + 0.25(D − D) (3.2)

WhereD = 1hrstormdurationand D = .∴ = . = 1.82hrs


19

1. for 1hr storm duration, Basin lag time= 10 + 0.28(1 − 1.182)= 9.80hrs2. for 2hr sstorm duration, Basin lag time= 10 + 0.28(2 − 1.182)= 10.05

The same procedure was followed for storm duration of 3 to 10hrs and the

value of basin lag time obtained are presented in Table 3.2.

3.2.1.3Peak discharge PQ

The peak discharge '

78.2

L

pp t

ACQ (3.3)

Where A is the catchment area, is the basin lag time for each storm duration

and is a storage coefficient varying from 0.4 to 0.8 (Suresh, 2005). An

average value of 0.6 was used for .

1. pQ for 1hr storm duration8.9

5736.078.21

pQ

smQp /53.97 31

2. pQ for 2hrs storm duration05.10

5736.078.22

pQ

2pQ = 95.10 /The same procedure was followed for storm duration of 3 to 10hrs and the

values of peak discharge obtained are presented in Table 3.2


20

Table 3.2 Synthetic unit hydrograph parameter for10hrs storm duration

D Tl Qp qp Tb W50 W75

(hr) (hr) (m3/s) (m3/s/km2) (hr) (hr) (hr)

1.0 9.80 97.53 0.170 101.52 39.99 23.05

2.0 10.05 95.10 0.166 102.15 41.03 23.65

3.0 10.30 92.80 0.162 102.90 42.13 24.94

4.0 10.55 90.60 0.158 103.65 43.28 24.94

5.0 10.80 88.50 0.154 104.40 44.50 25.64

6.0 11.05 86.50 0.151 105.15 45.45 26.19

7.0 11.30 84.58 0.148 105.90 46.45 26.77

8.0 11.55 82.75 0.144 106.65 47.84 27.57

9.0 11.80 81.00 0.141 106.65 48.94 28.21

10.0 12.05 79.32 0.138 108.15 50.09 28.87

3.2.1.4 Peak discharge per unit area

The value of peak discharge per unit area is presented mathematically as

(3.4)A

Qq p

p

Where is the peak discharge and A is the catchment area.

1. for 1hr storm duration is= = 97.53 3/573 2= 0.170 / /2. for 2hrs storm duration is= = . /

= 0.166 / /The same procedure was followed for storm duration of 3 to 10hrs and the

values of peak discharge per unit area obtained are presented in Table 3.2


21

3.2.1.5 Base time

For a small watershed, the base time is determined by multiplying by a value

ranging from 3 to 5 (Ward, 2004). Therefore, for this study,= 3 + ʹ(3.5)

1 for 1hr storm duration

880.931 bT

daysTb 27.41 .52.101 hrs

2 for 2hrs storm duration

805.1032 bT = 4.29 ≅ 102.15 .

The same procedure was followed for storm duration of 3 to 10 hrs and the

values of Base time obtained are presented in Table 3.2

3.2.1.6 Width estimation of unit hydrograph

It is possible to sketch many UHs through three known characteristic points of

the UH (i.e , , ) with its specific criteria i.e the area under the

synthetic unit hydrograph to be unity. To overcome this ambiguity associated

with the Snyder’s method, the US Army Corps of Engineers developed

empirical equation between widths of UH of 50% and 75% of i.e W50 and

W75 respectively as a function of expressible as

W50= 770( )-1.08 ; W75 = 440( )-1.08 Where 770 and 440 should be replaced

with 5.9 and 3.4 when metric unit system are used (Bhunya, 2011).


22

1. for 1hr storm duration

W50 = .. = .. .W50 .99.39 hrs

W75 = .. = .. .W75 .05.23 hrs

2. for 2hrs storm duration

W50 = .. = .. . = 41.03W75 = .. = .. . = 23.65

The same procedure was followed for storm duration of 3 to 10 hrs and the

values of base width of unit hydrograph obtained are presented in Table 3.2

3.2.2 Soil Conservation Service (SCS) Method

The SCS dimensionless hydrograph arbitrarily has units of 100 units of flow for

the peak and 100 units of time for the duration of flow. The area under

dimensionless hydrograph has 2620 square units of runoff. The SCS

hydrograph has 19 constant ordinates that represent the percentage of flow

and time (Uditha, 2011).

The following procedures are used to derive the design hydrograph

(Uditha, 2011):

(i) The Lag time ( ) can be estimated from the watershed characteristics

using curve number (CN) procedure as= 5.07.

7.08.0

1410486.222540YCN

CNLo

(3.6)


23

Where is the lag time in hours; L is the hydraulic length of watershed in (m);

CN is the curve number (50 ≤ 95); and Y is the average catchment slope in

(m/m) (Bhunya, 2011). With the CN = 75 based on soil group B, lowest runoff

potential, includes deep sands with very little silt and clay

(Ayanshola et al., 2009).

5.07.0

7.08.0

003.075141047586.22254048300

= .. hrs76.38

(ii) Duration of rainfall excess D = . (3.7)= .. = 7.047(iii) Time to peak

Tp = tL + (3.8)

Tp = 38.76 +.

Tp = 42.28 hrs.

(iv) Time to recession

trc= 1.67tp (3.9)= 1.67 × 42.28= 70.61(v) Peak discharge in ⁄= . ( ) = . ×. (3.10)= 28.19 ⁄


24

(vi) Peak discharge per unit area (qp).= = .(3.11)= 0.0492 /⁄

(vii) Base time Tb in hrs.= + (3.12)= 42.28 + 70.61= 112.89(viii) Runoff volume V in= = . × .

(3.13)= 2.78 km3.2.2.1 Conversion factors

There are three sealing factors used in the dimensionless hydrograph. These

factors include (Uditha, 2011):

(i) The ratio of the total runoff volume to the area under dimensionless

hydrograph u.= = .(3.14)= 1.06 × 10 .⁄

(ii) The second factor is w and is the ratio of the peak runoff for the

design storm to the peak flow of 100 units on the dimensionless

hydrograph, generally found with the SCS peak flow equation.

(Uditha, 2011). Expressed as= = .(3.15)= 0.2819 /⁄


25

(iii) The third factor k, is the value that each unit of time on the

dimensionless hydrograph represents in the design hydrograph. Thus= = × . ×. (3.16)= 0.63 ⁄The coordinate of the design hydrograph are obtained by multiplying the flow

and time ordinate of the dimensionless hydrograph by ‘w’ and ‘k’ respectively,

as shown in Table 3.3. The values for ‘w’ and ‘k’ are used to plot the unit

hydrograph curve as presented in Figure3.2.

3.2.3 Development of Design Storm Hydrograph

The established unit hydrograph ordinates were used to develop the storm

hydrographs due to actual rainfall event over the watershed. Peak storm

hydrograph for 50yrs return period was developed through convolution. The

maximum 24-hr rainfall depths of the different recurrence interval for the

catchment under consideration are 144.99mm (Salami et al., 2010). The storm

hydrograph was derived from a multi-period of rainfall excess called

hydrograph convolution. It involves multiplying the unit hydrograph ordinates

(Un) by incremental rainfall excess (Pn), adding and lagging in a sequence to

produce a resulting storm hydrograph. Table 3.3 was developed from the

convolution of the unit hyrograph from which Figure 3.2 was ploted using

column 9 againts column 1.


26

Table 3.3 Storm hydrograph ordinate for Oyun watershed

UH StormTime Ordinate P1Un P2Un P3Un P4Un P5Un P6Un Hydrograph(hr) Un

(m3/s)Qn (m3/s)

0 0.00 0.00 0.003 7.00 0.06 0.00 0.066 15.00 0.14 32.57 0.00 32.709 20.00 0.18 69.79 19.16 0.00 89.1312 21.00 0.19 93.05 41.07 7.14 0.00 141.4515 19.00 0.17 97.70 54.75 15.31 4.79 0.00 172.7218 17.00 0.15 88.40 57.49 20.41 10.25 3.85 180.5621 15.00 0.14 79.09 52.02 21.43 13.67 8.26 174.6124 13.50 0.12 69.79 46.54 19.39 14.36 11.01 161.2127 12.70 0.11 62.81 41.07 17.35 12.99 11.56 145.8930 11.50 0.10 59.09 36.96 15.31 11.62 10.46 133.5433 11.00 0.10 53.50 34.77 13.78 10.25 9.36 121.7636 10.00 0.09 51.18 31.48 12.96 9.23 8.26 113.2039 9.60 0.09 46.53 30.11 11.73 8.68 7.43 104.5842 9.00 0.08 44.66 27.38 11.22 7.86 6.99 98.2045 8.50 0.08 41.87 26.28 10.20 7.52 6.33 92.2948 8.00 0.07 39.55 24.64 9.80 6.84 6.06 86.9551 7.50 0.07 37.22 23.27 9.18 6.56 5.51 81.8154 7.00 0.06 34.89 21.90 8.67 6.15 5.29 76.9757 6.50 0.06 32.57 20.53 8.16 5.81 4.96 72.0960 6.00 0.05 30.24 19.16 7.65 5.47 4.68 67.2663 5.80 0.05 27.92 17.80 7.14 5.13 4.41 62.4466 5.20 0.05 26.99 16.43 6.63 4.79 4.13 59.0169 4.80 0.04 24.19 15.88 6.12 4.44 3.85 54.5472 4.30 0.04 22.33 14.24 5.92 4.10 3.58 50.2175 3.90 0.04 20.01 13.14 5.31 3.96 3.30 45.7678 3.40 0.03 18.15 11.77 4.90 3.55 3.19 41.5981 3.00 0.03 15.82 10.68 4.39 3.28 2.86 37.0684 2.50 0.02 13.96 9.31 3.98 2.94 2.64 32.8587 2.00 0.02 11.63 8.21 3.47 2.67 2.37 28.3790 1.80 0.02 9.31 6.84 3.06 2.32 2.15 23.7093 1.00 0.01 8.37 5.48 2.55 2.05 1.87 20.3396 0.80 0.01 4.65 4.93 2.04 1.71 1.65 14.9999 0.20 0.00 3.72 2.74 1.84 1.37 1.38 11.04102 0.93 2.19 1.02 1.23 1.10 6.47105 0.00 0.55 0.82 0.68 0.99 3.04108 0.00 0.20 0.55 0.55 1.30111 0.00 0.14 0.44 0.58114 0.00 0.11 0.11117 0.00 0.00


27

Figure 3.2: A plot of 50-yr, 24-hr storm hydrograph

The equation that apply to the SCS curve number method are given by= ( )( ) (3.17)

In which Qd is the runoff depth, P is the precipitation (maximum potential

runoff), S is the potential maximum watershed retention, Ia is initial abstraction

(Suresh, 2005).The initial abraction (Ia) is approximated by the following

empirical equation

)(2.0 mmSI a

Thus = ( )( . ) (3.18)

S is related to the soil and cover condition of the watershed through the CN.

CN is ranged from 0 to 100, and S is related to CN by= − 254 (3.19)

With CN = 70 based on soil group A, lowest runoff potential, includes deep

sands with very little silt and clay (Salami, 2010). S is estimated as 112.86 mm,

while Ia is 22.57 mm. This implies that any value of rainfall less than 22.57 mm

is regarded as zero. The storm hydrograph ordinate for the watershed due to

0.0020.0040.0060.0080.00100.00120.00140.00160.00180.00200.00

0 15 30 45 60 75 90 105 120

Stor

m h

ydro

grap

h flo

ws,

Q (m

3 /s)

Time (hr)


28

SCS method were extracted and used to plot the design hydrograph as

presented in Figure 3.3.

Table 3.4 Coordinates of the design hydrograph from SCS method

Points Time Flow Design Designordinate ordinate hydrograph hydrograph(t) (q) (k*t) (w*q)

1 0 0 0 0

2 2 3 1.26 0.8457

3 6 19 3.78 5.5361

4 8 31 5.04 8.7389

5 12 66 7.56 18.6054

6 14 82 8.82 23.1158

7 16 93 10.08 26.2167

8 18 99 11.34 27.9081

9 20 100 12.60 28.1900

10 22 99 13.86 27.9081

11 24 93 15.12 26.2167

12 26 86 16.38 24.2434

13 30 68 18.90 19.1692

14 34 46 21.42 12.9674

15 38 ` 33 23.94 9.3027

16 44 21 27.72 5.9199

17 52 11 32.76 3.1009

18 64 4 40.32 1.1276

19 100 0 63.00 0

Source: Bhunya, (2011).

The unit hydrograph can be used to determine the direct runoff hydrograph

for any rainfall amount with any time distribution. When it is needed to derive

the time-discharge curve due to multiple storms when storm duration is nT


29

(n is integer) use proportionality and principle of superposition to get the total

hydrograph, this process is called convolution (Uditha, 2011).

Figure 3.3: Hydrograph curve showing a plot of discharge againt time

3.3 Design of Concrete Weir

3.3.1 Water Pressure on Overflow Section

W1 = 1.2m

Height (H2) = 2.5m

Hydraulic head (H1) = 0.3m

Peak discharge: using the Snyder peak discharge of Q = 180.56 m3/s

Va = where (3.20)

Area A = 30 × 0.3A = 9 m2

0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Qisc

harg

e(m

3 /s)

Time duration (sec)


30

The velocity head of the water is estimated as

Va= .Va= 20.06 m s⁄water head = V2g = 20.062 × 9.81 = 1.02m

Total height = 2.5 +1.02

= 3.52m

w1

w2

gvH a

a 2

2

oT.E.L

H2

H

H1

aw HH 1

aw HH 2

W.S

PH

UPFigure 3.4 concrete weir section and pressure diagram


31

3.3.2 Estimation of Water Pressure and Overturning Moment

2.5m A B 0.3m

C 1.0m

2.0m

0.8m

Figure 3.5 concrete weir section divided into three sections

Horizontal component of the force due to water pressure per unit length of the

weir PHP = γ (H + H )H + (3.21)

2

2.59.812.51.020.39.81P2

H

= 63.03

Point at which PH act at

z =

a

a

HHHHHHHH

232

31

12

1212

02.123.052.3

3.033.0252.33.052.331z

z =86.502.507.1

z =0.92Overturning Moment Mo

Mo = PH* z (3.23)

Mo = 63.03 × 0.92 = 57.96 KNm

1.2m

(3.22)


32

3.3.3 Force due to Self weight and Resisting Moment

The concrete weir section is divided into three parts as shown in Figure 3.5

1. Part A

Weight of the section W (kN)

W = force × area

W = 24 × 2.5 × 1.2W= 72Moment arm (m)= × 1.2 + 0.8= 1.4m

Resisting moment Mr= ×= 72 × 1.4= 100.8 m

2. Part B

Weight W (KN)=

5.15.0

2124= 9

Moment armm= × 0.5 + 0.3= 0.63Resisting moment Mr= 9 × 0.63= 5.7


33

3. Part C

Weight W (KN)= 24 × 1 × 0.8= 19.2Moment armm= × 0.8= 0.4Resisting moment Mr= 19.2 × 0.4= 7.68

Table 3.5 Forces due to self-weight and resisting moment

Parts weights moment arm resisting moment(KN) (m) ( )

A 72 1.4 100.8B 9 0.63 5.7C 19.2 0.4 7.68∑ = 100.2 ∑ = 114.183.3.4 Stability Analysis

1. Overturning stability Fos= ∑ = .. (3.24)= 1.97Since 1.97 > 1.5, then overturning stability is o.k


34

2. Sliding stability Fss=HP

w

=03.63

2.10075.0 = 1.19Since 1.19> 1.0, then sliding stability is o.k

3. Centroid= ∑ × (3.26)= . . ×= 0.744. Eccentricity= − (3.27)= − 0.74= 0.26

= 0.26m which is less than 1, this implies that there is no tension in the weir.

Therefore the dimensions of the concrete weir are adequate as follows

Top width w1 = 1.2m

Top base width w2 = 0.5m

Base height = 1.0m

Height of the weir = 2.5m

Base width = 2m

Angle made by the downstream side to the vertical ∅ = 18

(3.25)


35

3.3.5 Uplift Force on the Base of the Concrete Weir

Case 1: when there is water at downstream side= + ( − ) (3.28)= 2 , = 0.3 , = 2.5 = 9.81 ⁄= 9.81 × 0.3 × 2 + × 9.81(2.5 − 0.3)2= 27.47Act at a distance

BHHBH

BBHHBBHz

11

11

21

32

2

8.273.4

z = 1.69 from the toe.

Figure 3.6 illustrate the uplift pressure diagram on the base of the dam when

there is water on the downstream side.

1.2m

2.5m 0.3m

B=2.0m

Figure 3.6 uplift pressure diagram when there is water on the downstream side.

1.0m

UP

(3.29)


36

Case II: When there is no water at downstream side= (3.30)= × 9.81 × 2.5 × 2= 24.533.3.6 Uplift Pressure in the Body of the Concrete Weir

At a depth 1.5m below the water surface as shown in figure 3.7 the width

b = 0.5m. Thus, the uplift force is given as= (3.31)= 9.81 × . × 0.5KNU p 68.3

And act at a distance 23( )

2×0.53

= 0.33m as shown in figue 3.7

Figure 3.7 Uplift pressure diagram in the body of the concrete weir

1.0m

1.2m

0.3m

B = 2.0m

UP

b = 0.5m2.5m 0.3m


37

3.3.7 Vertical Stress on the Concrete Weir

1. At the toe when reservoir is full

BBeW

Fyd

61

226.061

22.100

ydF

78.11.50ydF

2/18.89 mKNFyd

2. At the toe when the reservoir is empty

Be

BWFyd

61

226.061

22.100

ydF

2/02.11 mKNFyd

3.3.8 Principal and Shearing Stresses at the Toe

Principal stress at the toe

dydd f 2tan1

02 18tan118.89 d

2/6.98 mKNd

Shearing stresses at the toe

dydd f tan

018tan18.89 d

2/00.29 mKNd

The design parameters obtained from the analysis are presented in Table 3.6

(3.32)

(3.33)

(3.34)

(3.35)


38

Table 3.6 Design parameter for the concrete weir from the analysis

Parameters Values obtained

Approach velocity Va 20.06 m/s

Centroid 0.74 m

Concrete volume 177.3 m3

Depth due to approach velocity Ha 1.02 m

Eccentricity 0.26 m

Height of the weir H 2.5 m

Hydraulic area A 9.0 m2

Hydraulic depth 0.30 m

Length of overflow weir L 30.0 m

Overturning moment Mo 57.96 KNm

Principal stress d 98.6 KN/m2

Shear stress d 29.00 KN/m2

Uplift force: case I 27.47 KN

Uplift force: case II 24.53 KN

Vertical stress when reservoir is empty 11.02 KN/m2

Vertical stress when reservoir is full 89.18 KN/m2

Water pressure PH 63.03 KN

3.4 Concrete Volume

Volume A = 2.5 × 1.5 × 3 = 112.5Volume B = 0.5 × 0.5 × 1.5 × 30 = 11.25Volume C = 0.8 × 1.0 × 30 = 24Total volume of the concrete weir = 147.75Total volume of concrete using a 20% waste and shrinkageTotal volume of concrete = 0.2 × 147.75+ 147.75 = 177.3


39

3.5 Preparation Of Bill Of Quantity

The following price quotation was gotten from PPU (2012).

1. Concrete (1:3:6) = N 25,000/m3

2. Concrete (1:2:4) = N 28,000/m3

3. Excavation = N 500/m3

4. Formwork = N 1200/m2

5. Preliminaries = N 500,000

3.5.1 Quantity computation

1. Excavation = 1.0 × 2.45 × 30 = 73.52. Concrete blinding (1:3:6) = 0.05 × 2.45 × 30 = 3.6753. Formwork = 2(2.5 × 30 ) = 1504. Concrete (1:2:4) = 177.3m3

Table 3.7 Bill of Engineering Measurement and EvaluationS/No DESCRIPTION QTY UNIT RATE

(N)AMOUNT inNaria

1 Allow for preliminaries to be dispenced asdirected

LOT 500,000 500,000

2 Demolition of existing weir and cart away LOT 80,000 80,000

3 Excavation for concrete base 73.5 m3 500 36,7504 Concrete blinding (1:3:6) 3.675 m3 25,000 91,8755 Formwork 150 m2 1200 180,0006 Plain insitu concrete (1:2:4) 177.3 m3 28,000 4,964,4007 Stone pitching LOT 250,000 250,000

Total 6,103,025Add 2% contingencies 122,060.5Add 5% VAT 305,151.25

Grand Total 6,530,236.75


40

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1 Results and Discussion

The Snyder method of analysis was used to derive the synthetic unit

hydrograph of 50yrs rfeturn periods while the storm hydrograph for the

watershed was estimated from convolution analysis as presented in

Tables 3.2 and 3.3 respectively. Furthermore, the soil conservation services

(SCS) method was also used to analyse the unit hydrograph and the results

obtained were presented in Table 3.4.

The Snyder and the soil conservation services (SCS) method shows that the

peak flows for the river are 180.56m3/s and 28.19m3/s respectively. The

maximum peak discharge obtained (180.56m3/s) was subsequently used in the

design of the concrete weir. Some of the design results obtained include the

approach velocity Va (20.06 m/s), overturning moment Mo (57.96 KNm),

principal stress ∅ (98.6 KN/m2), shear stress (29.00 KN/m2) uplift force Up

(27.47 KN), vertical stress when the reservoir is full (89.18 KN/m2) and water

pressure PH (63.03 KN). All other design results for the weir were presented in

Table 3.6.


41

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

The design parameters obtained as shown in Table 3.6 means that the

concrete weir section is stable since all the stability criteria are satisfied. The

total depth of water over the crest of weir is 1.02m at maximum discharge of

180.56 m3/s. This implies that about 29% different in the total depth of water

above the overflow weir with the selected dimensions of the concrete weir of

2.5m height and 1.2m top width. It is therefore concluded that the

construction of the concrete weir should be executed to improve the

productivity of the research fields through the usage of the stored water for

irrigation purposes.

5.2 Recommendation

It is recommended that the established unit hydrograph can be used to

determine peak flow and design parameters for other hydraulic structures

such as drainage, culvert and small bridges all within the Oyun River basin.

It is also recommended that stone pitching should be provided at the two sides

of the weir to prevent scouring of the two sides which might eventually leads

to leakage of the stored water. It is further recommended that desilting of the

weir shoud be done periodically to prevent overfilling of the weir by sand and

debris deposite.


42

REFERENCES

Ahmad, Z. (2004) Recent Advances in the Design of Trench Weir.Department of Civil Engineering, Indian Institute of Technology, Roorkee,India.

Arora, K.R. (2004) Irrigation, water power and water Resources Engineering.Standard Publishers Distributions, 1705-B, NAI SARAK, Delhi India.

Ayanshola, A.M., Salami, A.W., Olofintoye, O.O. and Abdulkadir, T.S. (2009)Development of Storm Hydrographs for Three Rivers within DrainageNetwork in Kwara State, Nigeria using Snyder’s Method. Department of CivilEngineering first annual conference paper, University of Ilorin, Ilorin,Nigeria

Bhunya, P.K., Panda, S.N. and Goel, M.K. (2011) Synthetic Unit HydrographMethod: A Critical Review. The Open Hyrology Journal (5)1-8. NationalInstitute of Hydrology, Roorkee, India.

Chanson, H. (2004) The Hydraulics of Open Channel Flow. 2nd editionButterworth-Heinemann, Oxford, UK.

Okeola, O. (2012) Civil Engineering Practice. A monograph on the basic CivilEngineering practice, Department of Civil Engineering, University of Ilorin,Ilorin, Nigeria.

Physical Planning Unit (2012) Personal communication with chief quantitysurveyor, Physical Planning Unit, University of Ilorin.

Ramirez, J.A. (2000) Prediction and modeling of flood hydrograph andhydraulics. Chapter 11 of Inland flood hazards: Human, Riparian andAquatic Communities. Edited by Ellen Wohl; Cambridge university press.

Sturm, T.W. (2001) Open Channel Hydraulics. Water Resources andEnvironmental Engineering Series, McGraw Hill, Boston, USA.


43

Sule, B.F., Salami, A.W., Bilewu, S.O., Adeleke, O.O. and Ajimotokan, H.A.(2011) Hydrology of River Oyun and Hydropower Potential of Unilorin Dam,Ilorin, Kwara State, Nigeria. New York Science Journal 4(1):69-78.(http://www.sciencepub.net/newyork).

Suresh, R. (2005) Watershed Hydrology (Principle of Hydrology). Secondrevised edition, standard publisher distributors, Nai-sarak, Delhi India.

Uditha R. (2011) Engineering Hydrology (CE 205). Lecture note, Departmentof Civil Engineering, University of Sri Lanka.

www.wikipedia.org/weir (December, 2011).

Documents

DESIGN OF AN OVERFLOW CONCRETE WEIR FOR UNIVERSITY OF