CHAPTER THREE
RESEARCH METHODOLOGY
3.0 Location of Assessment of Water Drainage Structure in Iworoko-Ekiti
Iworoko-Ekiti is a semi-urban settlement located in Irepodun/Ifelodun Local Government Area
of Ekiti State, Southwestern Nigeria. It lies approximately 10 kilometers northeast of AdoEkiti, the state capital, and is situated along the Ado–Iyin–Ifaki expressway. Geographically,
the town is positioned between latitude 7°42′N and longitude 5°18′E, and covers an estimated
area of about 6.5 square kilometers. Iworoko Ekiti shares boundaries with Are-Ekiti to the
north, Ado-Ekiti to the south, and Iyin-Ekiti to the west. The nearest river to Iworoko Ekiti is
the Elemi River, which flows across the Ado-Iworoko road. It is also sometimes referred to as
Odo Ayo in that area. The Elemi River originates in Igede Ekiti and passes through the land of
Ekiti State University, near Iworoko. Name: Elemi River (also known as Odo Ayo), Location:
Flows across the Ado-Iworoko road and passes through the Ekiti State University area, Origin:
Begins as a natural spring in Igede Ekiti.
Topographically, Iworoko-Ekiti exhibits a gently undulating terrain with elevation varying
between 350 to 500 meters above sea level. The slope pattern generally runs toward the western
and southwestern parts, guiding natural drainage toward the Ureje River. The soil composition
is predominantly lateritic, with occasional clayey patches, which limits infiltration and
promotes surface runoff during heavy rainfall.
The climatic condition of the area is typically tropical wet and dry, characterized by distinct
rainy (April–October) and dry (November–March) seasons. The mean annual rainfall ranges
from 1,300 to 1,700 mm, and the average temperature ranges between 25°C and 30°C (Ayoade,
2016). These climatic characteristics make the area prone to intense surface runoff during the
wet season, which exerts pressure on existing drainage systems.
In recent years, Iworoko-Ekiti has experienced significant urban expansion, largely due to its
proximity to Ekiti State University (EKSU). The influx of students, staff, and commercial
activities has resulted in a growing population and increased built-up areas. This development
has altered the natural drainage pattern, replaced vegetated surfaces with impermeable
materials (such as asphalt and concrete), and increased the quantity of stormwater generated
within the town.
MAP OF IWOROKO-EKITI
3.1 Typical Drainage structure
1. Surface Drainage
This helps remove runoff water from the ground surface.

Shallow channels / gutters – Direct water into larger drains.

Roadside drains – Collect water from roads.

Open concrete drains – Common in urban areas.
2. Subsurface Drainage
Used to control groundwater beneath the soil surface.

Perforated pipes (French drains)

Soakaways

Underdrains around buildings
3. Stormwater Drains
Carry large volumes of water from rainfall.

Stormwater inlets

Manholes

Underground pipelines
4. Culverts
Structures that allow water to flow beneath roads or pathways.

Pipe culverts

Box culverts

Slab culverts
5. Channels & Waterways
For conveying water to natural outlets.

Concrete-lined channels

Earthen channels

Ditches
6. Erosion Control Structures
Prevent damage to the environment.

Riprap stones

Check dams

Vegetation lining
Purpose of a Drainage System

Prevent flooding

Protect roads and buildings

Control erosion

Improve sanitation

Enhance environmental safety
A diagram of a typical drainage system
Environmental factors that affect water-drainage structures in Iworoko-Ekiti
Heavy seasonal rainfall / intense storms
o
Iworoko (and Ekiti State generally) has a long rainy season with intense
downpours that often trigger surface runoff exceeding local drain capacity,
Implication: design drains and culverts for peak short-duration flows (not just
average rainfall) and provide emergency overflow routes.
Local topography and geology (rocky, heavily weathered basement complex)
o
The area sits on Precambrian basement rocks (granite/gneiss, migmatite) that
are deeply weathered in places; this controls infiltration, slope stability and
channel behaviour. Hard rock outcrops create steep slopes and concentrated
runoff paths.
o
Implication: drainage routing must follow natural channels; slope protection
and erosion control (check-dams, riprap, veg.) are often needed where bedrock
and soil interfaces occur.
Blockage from solid waste and poor sanitation practices
Blocked drains drastically reduce conveyance capacity and cause ponding/flooding.
Implication: establish scheduled desilting, community waste-management
programmes and public awareness to keep channels clear.
Insufficient or poorly-maintained drainage infrastructure
Culverts overtopped or damaged during floods often because infrastructure is
undersized or poorly maintained.
Implication: audit existing assets, prioritize upgrades to high-risk spots, and set up
routine inspection & maintenance protocols.
Vegetation removal and soil erosion upstream
Deforestation and vegetation clearance (for farming, building) expose soils to
erosion; sediments then reduce channel capacity and accelerate siltation of drains.
Implication: upstream reforestation, buffer strips, and gully stabilization reduce
sediment load downstream.
Poorly sited structures and informal development in floodplains
Buildings, market stalls and other structures built in natural flow paths reduce
conveyance area and funnel water into populated zones. News items from
Iworoko/Ado-Ekiti highlight structures affected by floods.
Implication: enforce setbacks, remove/relocate at-risk informal structures, and use
zoning to protect natural channels.
Iworoko Ekiti Residents Experience Major Flood
Human Factors Affecting Water Drainage Structures in Iworoko-Ekiti
1. Improper Waste Disposal
A major human factor affecting drainage performance in Iworoko-Ekiti is the common practice
of dumping household refuse, plastics, food waste, and market waste directly into open drains.
This leads to blockage, reduced flow capacity, and frequent flooding during rainfall.
2. Lack of Regular Maintenance of Drainage Channels
Many existing drainage channels are not periodically cleared of silt, vegetation, and debris.
Without scheduled maintenance, drains become shallow and less effective over time, resulting
in overflow and waterlogging.
3. Building on Natural Water Channels and Setbacks
Some residents construct buildings, shops, kiosks, and fences on natural waterways and
drainage setbacks. This obstructs flow paths, reduces the width of channels, and forces water
into streets and nearby homes.
4. Rapid and Uncontrolled Urban Development
Population growth and expansion of residential areas in Iworoko-Ekiti have increased
impermeable surfaces such as roofing sheets, paved compounds, and concrete roads. Without
sufficient planning, this increases stormwater runoff beyond the capacity of existing drains.
5. Poor Urban Planning and Enforcement
Weak enforcement of development regulations allows:

Construction in flood-prone areas

Failure to follow proper layouts

Lack of drainage provisions in new constructions
This results in undersized or incomplete drainage networks.
6. Lack of Public Awareness
Some residents are unaware of the impact of their activities on the drainage system. Low
environmental education means habits like indiscriminate dumping of waste, unregulated sand
excavation, and poor sanitation continue unchecked.
7. Low Community Participation in Drainage Management
Many see drainage maintenance as the sole responsibility of government. Low community
engagement reduces collective efforts such as voluntary clearing of drains before rainy seasons.
8. Poor Construction Practices
Some drainage structures are poorly designed or not built to standard due to:

Use of low-quality materials

Lack of qualified engineering supervision

Cost reduction by contractors
This leads to weak drains that crack, collapse, or silt easily.
9. Sand Mining and Soil Disturbance
Unregulated removal of soil and sand around the community increases erosion and sediment
flow into drains, reducing their depth and capacity.
10. Poor Land-Use Practices
Agricultural activities close to drainage channels, bush burning, and clearing of vegetation
increase soil erosion and introduce sediments into drains, speeding up blockages.
3.2 Existing Drainage Systems in Iworoko-Ekiti
The drainage infrastructure in Iworoko-Ekiti can be broadly categorized into natural drainage
and artificial (man-made) drainage systems.
3.2.1 Natural Drainage System
The natural drainage system consists mainly of small streams and rivulets that converge into
the Ureje River. These natural channels form the primary outfall for stormwater within the
town’s catchment. However, over the years, human encroachment and waste disposal have
degraded these channels. Many of the natural stream courses have been narrowed, obstructed,
or converted into refuse dumps.
The original catchment pattern, as derived from topographic maps, shows that the town drains
westward toward the Ureje basin. The natural slope provides good potential for gravity flow,
but poor maintenance and human interference hinder the effective use of this advantage.
3.2.2 Artificial Drainage System
The artificial drainage network includes roadside drains, concrete channels, culverts, and
gutters. Field investigation revealed three main types:
1. Open Concrete Drains:
These are the most common type, located along major roads such as the EKSU Road,
Market Road, and the main expressway. Most are rectangular or trapezoidal channels
made of reinforced concrete. Some are shallow (depth < 0.4 m) and narrow, limiting
flow capacity. Many are partially or completely blocked with silt and solid waste.
2. Unlined Earthen Drains:
Found mostly in residential areas and minor streets, these drains are unlined, irregular
in shape, and prone to erosion and collapse. During heavy rainfall, runoff erodes the
walls, increasing sediment load downstream.
3. Culverts and Cross Drains:
These structures connect channels under roadways. Field observations show several
culverts of various sizes, many of which are undersized or damaged. For example, the
culvert near the Market Junction experiences frequent overflow during storms due to
insufficient capacity.
4. Stormwater Inlets and Outfalls:
The town lacks an organized system of stormwater inlets or defined outfall points.
Most drains terminate abruptly or discharge onto open lands, creating pools of
stagnant water.
3.2.3 Condition Assessment of Existing Drains
A qualitative assessment was conducted using field observation and photographic evidence.
Drains were evaluated based on parameters such as alignment, blockage, structural integrity,
and maintenance level.
Parameter
Observation
Remark
Alignment
Many drains poorly aligned with natural Reduces flow efficiency
slope
Blockage
Frequent blockage by solid waste and silt
Major cause of overflow
Structural
Some channels cracked or collapsed
Requires reconstruction
Infrequent cleaning by local authority
Poor
Integrity
Maintenance
overall
performance
It was observed that over 60% of the drainage channels in Iworoko-Ekiti are partially
functional. Some newly constructed drains near EKSU are in better condition but lack
connectivity to downstream outfalls.
3.2.4 Socio-Environmental Impact of Existing Systems
The inefficiency of the existing drainage network results in several environmental problems:

Frequent flooding of roads and residential areas.

Erosion of unlined channels.

Health hazards due to stagnant water serving as breeding sites for mosquitoes.

Road damage from water stagnation and undermining of pavements.

Loss of property and farmland during heavy rainfall events.
These findings confirm that the current drainage system in Iworoko-Ekiti is inadequate for
handling the volume of stormwater generated within the catchment area, particularly during
peak rainfall periods.
3.3 Best Hydraulic Design
The best hydraulic design of a drainage structure is achieved when the system efficiently
conveys the design flow (runoff) without causing overflow, erosion, or sediment deposition.
The design must consider hydrological parameters, catchment characteristics, material
selection, and maintenance requirements.
3.3.1 Design Considerations for Iworoko-Ekiti
1. Catchment Area:
Based on field delineation, the average catchment area contributing to major drains in
Iworoko-Ekiti ranges from 0.5 to 2.5 km². Accurate catchment delineation is crucial
to estimating flow volume using the Rational Method:
Q=CiA
Where:
o
( C ) = runoff coefficient (0.6–0.9 for built-up surfaces)
o
( i ) = rainfall intensity (mm/hr)
o
( A ) = area (ha)
2. Rainfall Intensity:
From local meteorological data, design rainfall intensity for Iworoko-Ekiti is
approximately 100 mm/hr for a 10-year return period storm.
3. Slope and Topography:
Channel slopes should follow natural gradients between 0.005 – 0.015 (0.5%–1.5%)
to ensure self-cleansing velocity while preventing erosion.
4. Hydraulic Capacity:
Open rectangular concrete drains are suitable, with widths between 0.4 m – 1.0 m
depending on the flow rate. Channels must have freeboard (extra height above flow
level) of at least 0.15 m.
5. Material Selection:
Reinforced concrete or precast U-drains are ideal for durability and resistance to
erosion. Unlined earthen drains should be replaced with lined channels.
6. Inlet and Outlet Structures:
Proper inlets (grated openings) should be installed at regular intervals to collect runoff
from streets. Outfalls should discharge into natural channels or retention basins to
control peak discharge.
7. Maintenance Provisions:
Designs should incorporate access points (manholes) for desilting and cleaning.
Maintenance frequency should be quarterly, especially before and after rainy seasons.
3.3.2 Basic Principles of Hydraulic Design
Hydraulic design involves determining the size, shape, slope, and material of drainage channels
to ensure smooth flow. The fundamental equation guiding open-channel flow design is
Manning’s Equation:
Q = \frac{1}{n} A R^{2/3} S^{1/2}
Where:

( Q ) = discharge (m³/s)

( n ) = Manning’s roughness coefficient

( A ) = cross-sectional area of flow (m²)

( R ) = hydraulic radius (A/P)

( S ) = channel slope
This equation ensures that the designed channel has adequate capacity to handle stormwater
corresponding to a specific return period (commonly 10 or 25 years for urban drains).
3.3.3 Sustainable Drainage Design Approaches (SUDS)
Modern drainage design principles recommend integrating Sustainable Urban Drainage
Systems (SUDS) to mimic natural hydrology. For Iworoko-Ekiti, suitable SUDS techniques
include:

Permeable pavements to increase infiltration.

Vegetated swales to slow and filter runoff.

Retention ponds or constructed wetlands to temporarily store stormwater.

Rain gardens and soakaways around residential areas.
These systems reduce runoff volume, improve water quality, and enhance urban aesthetics.
They are also cost-effective when combined with conventional concrete drains.
3.3.4 Recommended Best Practice for Iworoko-Ekiti
The following are recommended design improvements for Iworoko-Ekiti drainage
infrastructure:
Parameter
Current Status
Channel Type
Open
concrete
Recommended Design Improvement
drains Deepened,
reinforced
rectangular
(shallow)
channels
Gradient
Irregular slopes
Uniform slope (0.5–1.5%)
Culverts
Undersized
Redesign for 10-year return flow
Outfall
Undefined
Connect to Ureje River via lined
channels
Maintenance
Irregular
Scheduled quarterly cleaning
Waste
Poor
Community waste bins and awareness
Management
By adopting these improvements, Iworoko-Ekiti can achieve a drainage network capable of
handling stormwater efficiently, reducing flood risk, and ensuring environmental
sustainability.
3.4 Summary of Methodology
This chapter presented the research methodology for assessing water drainage structures in
Iworoko-Ekiti. It discussed the location of the study area, identified major sources of
wastewater, analyzed the condition of existing drainage systems, and outlined hydraulic design
principles for effective drainage management.
The methodology integrates hydrological analysis, field observation, and hydraulic
computation to evaluate drainage performance within the catchment area.
CHAPTER FOUR
4.0
DISCUSSION
Assessment of water drainage structure in Iworoko-Ekiti should be seen as the act of practicing
maintenance culture and for this reason, the project will cover all the vital aspect of the drainage
problems stages.
The first stage of this project work shall include the reconnaissance survey of Iworoko-Ekiti,
noting the land scope and points ways, the effects of flood and erosion in the catchments area
and tributaries of the storms water that constitutes the major part of the erosion and flood
because it is quite noticeable that during raining season that most of the streets road leading
out to the main road are highly flooded.
The next is to find out the drainage system existing and the orientation, direction of the drainage
channels, the kind of hydraulic drainage design recommended for Iworoko Ekiti, its
serviceability and cost effectiveness of the method adopted shall be looked into.
4.1
PROBLEMS OF WATER DRAINAGE AND ENVIRONMENTAL IMPACTS
During rainfall, it has been observed that within Iworoko- Ekiti, the interception by vegetation
or by artificial surfaces such as roofs or pavements, fall on the earth either evaporates infiltrates
or lies in depression storage when the loses arriving in these ways within Iworoko areas are
also been provided for all, these may remain a surplus that obeying the gravitational law, flows
over the surface to the nearest stream channel at rectors village (“Wilson, 1983”). The flooded
water and effluent particular at the Social Justice Hostel hardly find their way to the channel
as a result of the absence of the drainage facilities, when the rain at Iworoko-Ekiti is particularly
intense or prolonged or both surplus run-off becomes large and the flooded water and effluent
cannot accept all the water suddenly arriving different angles they do great harm to the
activities of men around the area, its most effects resulted to erosion and run-off may act as the
washing away of the fertile top soil in which crops are grown and of which there is already a
scarcity on the earth. But mostly the best hydraulic design such as trapezoidal, rectangular
channel are recommended for the effective drainage system.
4.2
SOLUTION TO THE PROBLEMS
As a result of many problems associated with the water drainage problems at Iworoko-Ekiti,
adequate maintenance culture and the good channeling system should be practiced for effective
performance of the drainage system toward the bridge located at Unity road.
The maintenance system at Iworoko-Ekiti should be put in place right from the design and
construction stage up to the time when the drainage system is in full use as it has been designed
and also the procedure include the followings:
(i)
Provision of continuity reinforcement at the concrete joint
(ii)
Designing the structure for blocked outlets.
(iii)
The site must be adequately compacted against settlement and subsidence at the
construction stage.
(iv)
Adequate movement joints must be provided against ground movement and settlement.
(v)
The concrete must be adequately cured before the drainage is put into used, hence, form
work must also be adequately constructed to avoid grout leakage at joints and consequent areas
vulnerable to water penetration.
(vi)
Provision of access shall be required for inspection chamber.
(vii)
Clearing and testing must take account of safety and ventilation requirement,
(viii) Dumping of refuse and waste along drainage should be strictly prohibited
(ix)
Sealing of joints are expected to be done
(x)
Concrete should not be exposed to abrasive chemicals
(xi)
High vehicles and traffic should be allowed where access pass-over drainage channel
(xii)
Where erosion organics waste, urgent effort should be made to remove them to prevent
blockage of drainage channel
4.3
DESIGN AND CONSTRUCTIONAL SOLUTION
To ensure water tight structure within the community of Iworoko-Ekiti, the concrete must be
adequately reinforced in section where tension may occur. For this reason, it is important to be
able to envisage the deflected share of the structure and its individual elements. Tensile stresses
due to any direct tensile forces as those due to bending must be included in the design
calculations continuity reinforcement to prevent cracking within the community. This
reinforcement must extend well beyond where it is required to resist the tensile stresses,
particularly when these stresses occur on the face in contact with the liquid (water).
The design for Iworoko Ekiti community should be considered in the cases where the structure
is full of liquid thereby allowing for blocked outlet and also when it is empty. The structure
when empty must have the strength to withstand the active pressure of any retained earth, since
the passive resistance of the earth within community is never certain to be acting, it should
generally be ignored when designing the full structure. Cracking occur not only from flexure
shrinkage but also from subsidence. Careful attention must be given to the geological aspect of
unproposed site within the Iworoko Community and particularly to the possibilities of
differential settlement. It may sometimes be necessary to provide movements joints to take care
of this. In addition to expansion and contraction joints required to allow for thermal effects can
be reduced considerably by careful attention to the construction factors; with a thick section,
the heat generated by hydration cannot readily be dissipated. Cracking should thus be based on
maximum member thickness of 500mm thick. The bottom size zone for ground slabs should
only be 100mm. Temperature rises due to hydration must be arranged to allow for the core
temperature.
The impotence of good earring cannot be over emphasized, but it is importance to remember
that good compaction on site just as vital if not more critical in producing an impermeable
concrete. It is essential that the concrete mix used is sufficiently workable to enable easy
handling during construction with no tendency of segregation. An increased water content
combined with higher cement content will help to achieve this while a longer mixing time and
the use of natural aggregates in preference to crushed stone are also helpful. Wall thickness of
at least 200mm are recommended to assist compaction form work should also be carefully
constructed to avoid grout leakage at joints and consequent areas of concrete vulnerable to
water drainage system penetration within the campus, particular care must also be given to the
use form work ties, potential leakage path.
The choice of surface finishing should take account of possible stating of exposed surface at
various part of Iworoko community premises particularly during construction. It is a major
problems to overcome this, it may be necessary to dewater the site, increase the construction
sequence must be carefully studied and specified at the design stage to ensure a minimum factor
of safety against floatation, clearing and testing must take account of safety and ventilation
requirements within Iworoko Ekiti.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
5.0
RECOMMENDATIONS
Based on the method and approach used in the water drainage problems at Iworoko Ekiti
community in this project work, the followings are recommended.
(i)
Ordinary Portland cement (O.P.C) with little heat of hydration with good proportion of
water/cement ratio during mixing is highly recommend as this tends to reduce the cracks and
flows on the reinforced concrete structure.
(ii)
Standard concrete mix should be used within the areas with adequate quality control on
workability with no segregation when purring it as this will guarantee a water tight structure,
high resistance to wearing and scouring.
(iii)
The limit state of design under load and serviceability as well as the inspection chamber
should always be adopted because of its simplicity and safety
5.1
CONCLUSION
Conclusively, the project work has covered most of the fundamental principles on which the
water drainage problems systems at Iworoko Ekiti community are based. The critical analysis
of this project work shall simply show that the water drainage problems within Iworoko Ekiti
community which is the subject in quote should be strictly adhere to all principles and strategies
of water drainage system in this project.
Though some of the data, values and figures used in this project were based on the assumption
empirical values and even some of them were chosen just by the rule of thumb, but it will be
categorically stated here that most of this facts and figures are used in day to day principle and
should be applied of water drainage problems within Iworoko community with little or no
modification.