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From this study a pilot area of western part of Dhaka city called Goranchatbari will be modeled using open source tools named EPA SWMM 5.1


Description

Summary

Rainfall induced flooding during rainy season is a regular phenomenon in Dhaka City [1]. Almost every year a significant part of the city suffers badly with drainage congestion [1]. There are some highly dense areas with lower ground elevation which submerge under water even with an intense precipitation of few hours [1]. The higher areas also suffer with the drainage problem due to inadequate maintenance of the system and encroachment or illegal filling up of the drainage canals and lakes [1]. Most part of the city suffered from long term urban flooding during historical extreme rainfall events in September 2004, 2007 and July 2009 [2]. The situation is likely to be worsening in the future due to climate change, which may lead to more frequent and intense precipitation [2].

Storm-water drainage modeling has a major role in preventing issues such as flash floods and urban water-quality problems [3]. A good number of modeling tools are available around the world for hydrological and hydraulic analysis of urban areas like MIKE Urban, SOBEK, Bentley StormCAD, GeoSWMM and EPA SWMM [3]. Among all these tools, EPA SWMM [4] is an open source tools to study the urban drainage problems.

The present scenario of urban morphology of Dhaka city and existing drainage system is complex for hydrological and hydrodynamic modeling [5]. Several studies were carried out including modeling for drainage master plan of Dhaka city like: JICA Studies (1987), FAP 8A (1990), FAP 8B (1991), IWM Study (2006) and DWASA Study (2014) [6][7][8][9]. However still knowledge and solutions to the drainage problem for Dhaka city are limited. Therefore in this study a pilot area of western part of Dhaka city called Goranchatbari will be modeled using EPA SWMM.

 


Which proposals are included in your plan and how do they fit together?


Explanation of the emissions scenario calculated in the Impact tab


What are the plan’s key benefits?

OBJECTIVES WITH SPECIFIC AIMS AND POSSIBLE OUTCOME:

The broad objective of this study is to assess the effects of water logging and climate change with the rapid urbanization of Dhaka city. The specific objectives of the study are as follows:

·      To assess the existing drainage condition of the study area.

·      To set-up a Hydrological Model of the study area using SWMM.

·      To prepare flood inundation map of the study area for selected storm event.

·      To investigate the effects of climate change and land-use pattern for the study area.

 

Possible outcomes: The following output would be achieved through study:

·      Improved knowledge and understanding on the vulnerable factors affecting the water logging problems for the study area.

·      A Hydrological Model of study area using SWMM.

·      Inundation map of study area for different storm events and scenarios.


What are the plan’s costs?

No.   Item Name   Cost

a) Data collection, Conveyance 7000 USD

b) Paper, computer disk, cartridge,  Binding of thesis  etc. 3000 USD

c) Miscellaneous 1000 USD

Total:                                                                      Ten Thousands USD only.

10,000


What are the key challenges to enacting this plan?

DATA COLLECTION: The detailed area drainage model requires high spatial and temporal resolution data, including detailed information about drainage infrastructures. The necessary data will be collected from various sources like:

Data Source

Source

Topography (DEM)

Survey of Bangladesh

Meteorological

BMD, BWDB

Drainage infrastructure

DWASA, DCC, BWDB

Land cover

Dr. SarwarJahan (BUET)

River stage

BWDB

River flow

BWDB

River sections, slope, alignments

DWASA ,IWM

ASSESSMENT OF EXISTING DRAINAGE CONDITION OF GORANCHATBARI AREA: Existing drainage conditions of the study area will be assessed based on available collected data, previous reports and field visit. 


Timeline

PREPARING FLOOD INUNDATION MAP OF STUDY AREA: Flood inundation maps will be developed using GeoSWMM for different storm events and scenarios. Validation of inundation maps will be done by comparing with the LANDSAT images of the study area.

EFFECTS OF CLIMATE CHANGE AND LAND-USE CHANGES OF THE STUDY AREA:

Using the calibrated model, effects of climate change and land use change for the study area will be studied. Two potential scenarios will be modeled for the assessment of design storm.


Related plans

MODEL DEVELOPMENT AND CALIBRATION: The first step to set-up a SWMM model will be the catchment delineation which will be divided the total study area into small sub catchments according to the understanding of the drainage system and flow direction of storm-water. The existing study area stream network will be burn into the Dhaka digital elevation model (DEM) with ArcGIS 10.1which is a powerful tool for catchment delineation.The rain gauge station of Bangladesh Meteorological Department (BMD) will be used in this model. The sub catchment boundary will be imported from GIS Shape file. The parameter sub catchment width will be calculated from drainage network, sub catchment boundary and area. Percent of impervious and pervious area will be calculated from existing and future land use pattern and applied in sub catchment property. For other parameter standard values will be used.


References

REFERENCES

[1] Gain.A. K. and Hoque,M.M. (2012) “Flood Risk assessment and its application in the Eastern part of Dhaka city, Bangladesh.” Journal of Flood Risk Management. 

[2] Ahammed F. and Hewa G.A. (2012) “Development of hydrological tools using extreme rainfall events for Dhaka, Bangladesh”, Water International, 37:1, 43-52. 

[3] HenriTikkanen (2013) Hydrological modeling of a large urban catchment using a storm water management model (SWMM).

[4] Rossman Lewis A. (2010) “Storm Water Management Model” user’s manualVersion 5.0

[5] Dasgupta S., Selim S. and Tauhid S. (2012) “Urban Flooding of Greater Dhaka Area in a Changing Climate: Vulnerability, Adaptation and Potential Costs”, Concept Note, WB Dhaka.

[6] JICA (1987) “Study on Drainage master plan for Dhaka city”Japan International Cooperation Agency, Dhaka Water Supply and Sewerage Authority, Dhaka, Bangladesh.

[7] JICA (1990) “Master Plan for Greater Dhaka Protection Project, FAP 8A Main andSupporting Report, Government of Bangladesh.