DEPARTMENT OF CIVIL ENGINEERING

AHSANULLAH UNIVERSITY OF SCIENCE AND

TECHNOLOGY

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

Figure 1: Insufficient rain or No rain

condition

Figure 2: Over or excess rain water

condition

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.

The Study PurposeBy 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.

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

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).

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

A= flow area, m^2

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.

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

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.

The field surveyshows poorcondition of thecanal. Canal water fillwith algae's, wastesand unprotected.

Figure 5 sow thatThe canal water isalmost covered withgreen algae andturned black.

Black Water

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.

Figure 7 demonstratesthat sides of canal isdecorated and cleanbut lacks properplanning of drainingthe water out.

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.

Figure 9 points out to the conditionof Basundhara canal at the lastpoint of Block E. Photos are takenduring field survey and found thatthis part of canal is completelycovered with green algae.

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.

RAINFALLDesign 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.

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.

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.

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.

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

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

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.

Figure 6: Proposed final

layout containing different

zones and drainage network.

Cross Section of Drains: All units are in meter

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.

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

it simple and useful in the planning of storm drainage system in

Limitations of the work

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.