This document summarizes a study on the design of an urban drainage system for the Bashundhara Residential Area near Dhaka, Bangladesh. It includes the objectives of assessing the existing drainage, identifying future needs, and suggesting improvements. Key aspects of the study include: dividing the area into 16 drainage zones; estimating peak runoff using the Modified Rational Method; designing drain dimensions using Manning's equation; and proposing a layout involving primary, secondary, and sub-secondary drains to convey stormwater to outfalls. The study aims to provide approaches to understand urban flooding problems and find solutions.

1. DEPARTMENT OF CIVIL ENGINEERING
AHSANULLAH UNIVERSITY OF SCIENCE AND
TECHNOLOGY

4. The Project is prepared by
1.FATEMA SULTANA Student No: 10.01.03.159
2.MD. IBRAHIM BIN AZIZ Student No: 10.01.03.050
3. MD. IMRAN HOSSAIN Student No: 08.02.03.108
Special thanks to our supervisor
Dr. Quazi Hamidul Bari
Professor
Department of Civil Engineering

5. Figure 1: Insufficient rain or No rain
condition
Figure 2: Over or excess rain water
condition

7. objectives of the study:
The study is intended to assist in urban drainage management. The aim of this drainage
study is to assess the present drainage situation, identify the future requirements and
suggest suitable drainage network system .
The following specific objectives are required to be followed:
1) Analyzing the existing conditions related to drainage facility in urban area.
2) On the basis of outfall, dividing the total water shed into number of drainage zones
to check the discharging capacity of the outfalls.
3) Propose design of drainage network by construction of primary and secondary
drains.
4) Propose suitable outfalls layout to accommodate runoff from present and future
urbanized area.
This study aims to contribute ideal approaches to understand deeply urban flooding
problems which is related to heavy rainfall, i.e. to find the causes, to analyze their
propagations and on this basis to evaluate, and finally to search for solutions.

8. The Study Purpose
By abiding the following measures, proper urban drainage design is
possible.
1. Prevent water logging
2. Properly dispose of storm water.
3. Prevent environmental pollution such as stopping breeding of
mosquitoes, odor and nuisance etc.
4. Improve hygiene conditions of people.
5. Transportation system may improve which is very much affected
for poor drainage system.
It is very important to have a proper and modern drainage system for
the maximum welfare and prosperity of the city. The research study
aims to present a comprehensive view of the management of urban
rainwater, which includes proper urban drainage design.

9. Design Procedures follows the steps below-
Selecting the catchment
area
Collection of data
Estimating Flow in
every segment
Design for the cross
section of drains
Propose the
layout of
drainage network

10. DESIGN CRITERIA:
Modified Rational Method:
In designing primary and secondary drains of Study area the Modified
Rational Method is practiced. The runoff by Modified Rational Method is
shown in equation 1:
Peak runoff, Qp = (Cs*Cr*I*A)/360………………………………..Equation
1
Where; Qp = Peak runoff flow rate (m3/s)
I = rainfall intensity (mm/hr)
Cs= storage coefficient
Cr= runoff coefficient
A = catchment area (hectares).

11. MANNINGS’S EQUATION
The Manning formula is an empirical formula estimating the average
velocity of a liquid flowing in a conduit that does not completely
enclose the liquid, i.e., open channel flow. The Manning’s Equation is
used for calculation of flow velocity is given below. In determining
the dimension of drain, the criterion is that the design discharge (Qd)
should be greater than the peak runoff (QP). Manning’s equation is
shown in equation 2.
Design velocity, V = [1/n][R^2/3][S^1/2] …………………………….....Equation
2
& Design discharge, Qd =AV= A[1/n][R^2/3][S^1/2]…………………..Equation
3
Where,
V = velocity of flow, m^2/s
n = Manning’s roughness coefficient value
S = Hydraulic gradient, m/m
R = hydraulic radius=A/P, m

12. Time of concentration (Tc) is generally defined as the longest runoff travel
time for contributing flow to reach the outlet or design point, or other point of
interest. It is frequently calculated along the longest flow path physically. The
time of concentration is the sum of time of entry (Te) and travel time (Tt).
Time of entry is the time taken for runoff from the farthest point in the
contributing area to flow over the ground and enter into the drain. The time of
entry (Te) is estimated using Kirpitch Equation with the minimum time of entry
set as 4 minutes. The Kirpitch equation is:
Te = 0.019621L^0.77/S^0.385…………Equation 4
Where,
Te = time of entry in minutes
L = maximum length of overland flow in meter.
S = average ground slope
Travel time is the time taken for runoff to flow through the drain. Travel time
(Tt) is calculated by dividing the length of drain by the water velocity.

13. Study Area:
The study was conducted in
Bashundhara Residential Area
which is situated in the suburb of
Dhaka City, which is located
besides a Bashundhara canal. It
consists of an area of about 2.23
square km. This area is
developed by Bashundhara
authority, a private housing
organization. The landscape is
completely planned except some
regions in southern region where
no development is initiated yet.
Figure 3: Selected study area

14. Present Condition of Study Area:
A site visit of Basundhara Canal is done to evaluate the condition of Primary
Canal. Photos have been taken at six different points where the proposed
secondary drains will convey storm water to the Outfall.
Figure 4: Propose six different points to convey storm water to
Basundhara Canal.

15. The field survey
shows poor
condition of the
canal. Canal water fill
with algae's, wastes
and unprotected.

16. Figure 5 sow that
The canal water is
almost covered with
green algae and
turned black.
Black Water

17. Figure 6 contains photos on
both sides of Apollo Hospital
Road. Serious pollution, waste
damping have been observed.
These wastes are dumped in
the canal without any
awareness that it may pollute
canal water and hinder the
natural flow.

18. Figure 7 demonstrates
that sides of canal is
decorated and clean
but lacks proper
planning of draining
the water out.

19. Figure 8 consists the photos of Ahmad Akbar Sobhan Avenue Road. It is been
seen that the canal has become dry and narrow at this part due to waste deposition
in the canal.

20. Figure 9 points out to the condition
of Basundhara canal at the last
point of Block E. Photos are taken
during field survey and found that
this part of canal is completely
covered with green algae.

21. Data Collection:
Both primary and secondary data have been used in the present research. The information
sources were various organizations such as Flood Forecasting and Warning Centre
(FFWC), Bangladesh Meteorological department (BMD) Agargaon, Institute of Water
Modeling (IWM), Water Resources Planning Bangladesh (WARPO), Different Journals,
Articles, published research papers etc. Shape files for districts, Thana’s, rainfall stations,
roads, buildings, datum value, rivers, lakes, canals has been collected from DWASA.
RAINFALL
Design rainfall storm intensity for the Study area is used 150 mm/hr. The Rainfall
Data was collected from Bangladesh Meteorological Department, Agargaon with
reasonable length of 40 years records which is from 1970 to 2009. It is selected
as the reference station for assessment of storm intensity for Bashundhara
Residential Area. The average yearly rainfall is about 2043 mm.

22. Percentage of Average Annual Rainfall in
mm/hr
the last 40 years mean Monthly Average
Rainfall Data.
About 65% rainfall occurs during the period from June to September.

23. Figure 4: Proposed drainage Zone pattern.
The whole study area has
been divided into 16 zones or
areas for drainage design
purpose as shown in Figure 4
with the help of Arc GIS
9.3.They are designated as
Z1,Z2,Z3,Z4,Z5,Z6,
Z7,Z8,Z9,Z10,Z11,Z12,Z13,Z
14, Z15,Z16.

24. Figure 5: Proposed drainage line network pattern.
The proposed drainage network
consists of 16 different drain types
where there are 6 sub secondary
drains and 10 secondary drains. They
are P1S1S1,P1S1S2,P1S1S3,P1S2S1
,P1S2S2,P1S3S1,P1S11,P1S12,P1S13
,P1S14,P1S21,P1S22,P1S23,P1S24,P
1S31,P1S32. Storm water drainage
path is shown by red straight line in
the figure 5. The black straight arrow
lines show the water draining path
from sub secondary drains to main
secondary drains. The main secondary
drains collect water from sub
secondary drains and supply this water
to proposed primary drain,
Bashundhara canal. Then the runoff is
eventually carried toward the final
outfall.

25. Table1: Modified Rational Method for the calculation of peak discharge.

26. Table 2: Design of drain section using Manning’s Equation.

27. Proposed drainage layout:
The proposals for layout of drains are given below:
• P1S1S1, P1S1S2, P1S1S3 storm drains will drain runoff water from
some parts of Block C, Block B and Block A to secondary drains P1S11, P1S12,
P1S13 respectively. P1S11, P1S12, P1S13 main secondary drain will collect
storm water respectively from Block G, Block C and F, Block B and D and also
from sub secondary drains and convey to the primary drain P1. On the other
hand P1S14 will convey water to primary drain and also to the undeveloped
lower land side at the south.
• P1S2S1, P1S2S2, type drains will drain storm water runoff from some
part of Block G, Block F and Block D to main secondary drain P1S21 P1S22
respectively. Again, P1S21, P1S22, P1S23 secondary drains may convey runoff
water respectively from Block G, Block F, Block D and Block I to the canal.
P1S24 type drain may convey a little water to the Primary drain.
• P1S3S1 type sub secondary drain will drain runoff water from some
part of Block G and Block I. Then P1S31 and P1S32 main secondary drains will
convey storm water from large part of Block G and Block I and also from sub
secondary drain.
Drain lines network has been super imposed upon drainage zones or catchment
areas that are shown in figure 4 to give a clear and complete view of proposed
drainage layout.

28. Figure 6: Proposed final
layout containing different
zones and drainage network.

29. Cross Section of Drains: All units are in meter

30. Conclusion:
To sum up, the site visits, data collection and all the data analysis has been done
carefully though some shortcomings during data collection period.
• Suitable secondary drains and primary drain layout and design are proposed
in this study. Drain shapes are considered rectangular for the simplicity of the
calculation.
• In Manning’s Equation roughness coefficient is considered 0.014 for R.C.C
drains.
• A free board of 0.15 m is added to the depths of secondary drains and 0.2 m
for primary drain.
• To prevent sedimentation and vegetative growth, the minimum average flow
velocity shall not be less than 0.6 m/s.
• The maximum average flow velocity shall not exceed 4 m/s. The average flow
velocity in a grassed swale shall not exceed 2 m/s. If this is not practical, an
underground pipeline, lined open drain, or grass reinforcement system should
be provided.
• Trash racks should be used in the secondary drains at its inlet to prevent floating
debris and solid waste from entering into the drainage system. Another important
thing is silt trap. It should be installed to collect and reduce the obstructions to the
flow. Sufficient size of silt trap should be maintained.

31. Recommendation
• Secondary and primary drainage designs are the sole concern of this
study. Since the selected site has not developed completely yet,
tertiary drainage layout has not been included in the work. Since drains
will run under the streets sides, so road network have to be well
established for any selected study sites.
• Rainfall analysis of long length of periods such as 50 years or 100
years will provide more precise result of storm pattern for a designated
area.
• This study is limited to analytical calculation and GIS mapping. Model
simulation process could not be possible due to unavailability of
software’s at undergraduate level. Bentley Water CAD, Water Gems,
Storm CAD, Civil Storm all these modeling programs can be purchased
and used to analyze and design storm sewer systems using a peak
flow based on approach. The comparison between Analytical approach
result and Model based result may help to design the drainage system
with more excellence. GIS also has programming capabilities.
However, in this thesis the programming is limited due to lack of more
information and time.
• The study is conducted keeping in mind that researchers, urban land
use planners and municipal engineers in developing countries may find

32. Limitationsof thework
Some limitations were encountered during the study period in completing
work according to the selected objectives.
• The data mostly are scarce in perspective to research more about
hydrological condition of the study area. Very few studies were conducted
related to water logging and drainage system of Dhaka City. As a result,
there was no sufficient literature to enrich the analysis of this study by
reviewing their study findings.
• Lack of detailed road network data’s and elevation data’s were really a
problem. The unwillingness and unresponsive attitude of different
responsible authorities during data acquisition was really unexpected.
Hence it delayed the research work a little.
• In some cases, the study has been carried on depending on photograph
rather than numeric data to illustrate the causes of the situation.