Assessment of Drainage Congestion at Sylhet City of Bangladesh and Development of Stormwater Drainage Masterplan Using GeoSWMM Model (original) (raw)
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Climate change will affect water resources through its impact on the quantity, variability, timing, formation and intensity of precipitation. Improved management of storm water is critical, if addressed inadequately, it will jeopardize progress of poverty reduction targets and sustainable development in all economic, social and environmental dimensions. The purpose of this drainage study is to assess the present drainage situation, identify the future requirements and suggest improvement of the drainage network system to provide the Municipality a area free from water congestion within an acceptable environmental condition. Integrated study of drainage dynamics in consideration of gravity flow for the proposed drainage improvement system is made by developing rainfall-runoff model and analytical computation for the urbanized area. The overall planning processes are conjugated with rigorous study of infrastructure, Digital Elevation Model (DEM), land-use and sattelite image using GIS for a preliminary conceptual understanding of the Municipality system; identification of rivers/khals* surrounding the Municipality and collection of data to understand the hydrological response of the Municipality; assessment of effective range of land levels which would be considered for planning process; making of intensive field visit for identification of possible outfalls and drainage routes in verification of the preceding planning processes; planning of drains & zones with scrutinized outfall locations; and finally storm runoff assessment using empirical formula. Modelling approach is used to generate catchment runoffs which are calibrated against flows using empirical formula known as modified rational formula for respective design year.
Climate change will affect water resources through its impact on the quantity, variability, timing, formation and intensity of precipitation. Improved management of storm water is critical, if addressed inadequately, it will jeopardize progress of poverty reduction targets and sustainable development in all economic, social and environmental dimensions. The purpose of this drainage study is to assess the present drainage situation, identify the future requirements and suggest improvement of the drainage network system to provide the Municipality a area free from water congestion within an acceptable environmental condition. Integrated study of drainage dynamics in consideration of gravity flow for the proposed drainage improvement system is made by developing rainfall-runoff model and analytical computation for the urbanized area. The overall planning processes are conjugated with rigorous study of infrastructure, Digital Elevation Model (DEM), land-use and sattelite image using GIS for a preliminary conceptual understanding of the Municipality system; identification of rivers/khals* surrounding the Municipality and collection of data to understand the hydrological response of the Municipality; assessment of effective range of land levels which would be considered for planning process; making of intensive field visit for identification of possible outfalls and drainage routes in verification of the preceding planning processes; planning of drains & zones with scrutinized outfall locations; and finally storm runoff assessment using empirical formula. Modelling approach is used to generate catchment runoffs which are calibrated against flows using empirical formula known as modified rational formula for respective design year.
Assessment of Future Flow of Hatirjheel-Begunbari Drainage System due to Climate Change
Dhaka, the capital of Bangladesh, has experienced water logging for last couple of years as the storm water drainage systems are often unable to manage peak runoff volume. Moreover, precipitation intensity and pattern are expected to be altered due to climate change and such changes are likely to lead to severe flooding in urban areas of Bangladesh. This study aims to assess the effect of climate change on flow of Hatirjheel-Begunbari Khal storm water drainage system as it is considered one of the major drainage channels of Dhaka city. As Hatirjheel works as a large storm water detention area and also a regulatory system, different scenerios are considered while assessing the future flow. The rational fromula was used to assess the flow instead of hydrologic model due to lack of observed flow data for calibration and validation. The study involves DEM based catchment delineation using GIS. The DEM was reconditioned prior to catchment delineation to create a channelization effect intended to mimic the existing storm sewer network of the city. A future land use scenario is considered based on the analysis of land use maps of three different time interval for determining future runoff coefficient. The peak rainfall intensity is obtained from the IDF curve of Dhaka city developed considering the future precipitation data of a climate model. Although Hatirjheel is found to be an effective retention and regulatory system to minimize the flow, result of this study shows an alarming increase in flow in future which might cause severe flooding in the surrounding area.
A Hydrological Urban Drainage Model and Its Application – a Case Study
2018
Now a days, water-logging due to excessive rainfall is becoming more serious in urban areas making it necessary to urgently assess and redesign the existing draiage facilities to drain out the storm water more efficiently. In this study, a hydrologic urban drainage model is developed by combining Horton’s equation for the estimation of runoff losses and Manning’s equation for flow through drains to relate the rainfall-runoff respons. The existing drainage facilities for a typical urban catchment, Ward No. 22 in Khulna City Corporation of Bangladesh are studied, analyzed. To analyze the drainage characteristics efficiently, the study area is subdivided into 8 sub-catchments. It is found that the existing drainage facilities are not adequate for the study area and the water logging condition will be happend if a rainfall intensity is equalled or exceed 1.2 in/hr irrespective of the rainfall duration, no water logging condition will be occured below this level. It is concluded that the...
Impact of Climate Change on Urban Drainage Systems in Three Selected Coastal Towns of Bangladesh
2014
As urban growth is increasing in coastal zones, urban drainage system would suffer from additional stresses due to water logging. Moreover, climate change is to enhance natural disasters like floods and heavy rainfall events. So, urban drainage and its performance will be important issues in the coastal towns of Bangladesh. In this study, storm water management model (SWMM) has been used to assess the future possible drainage conditions for three selected towns of coastal areas – Amtali, Galachipa and Pirojpur. Design storm of 2-hour 10 year return period and design water level of surrounding rivers of 20 year return period were considered for simulation of drainage model. For future precipitation, high resolution climate change information has been generated using moderate emission scenarios SRES A1B derived by REGCM3 regional climate model. Sea level rise information from secondary sources has been added with 20 year return period to simulate the future scenarios. DEM of 10 m reso...
Modelling Urban River Catchment: A Case Study in Malaysia.
Water Management Journal
Generally, many rivers within urban catchments in Malaysia are being altered from their natural states to meet the demand of developments. Most of these rivers have also become the receiving water body for urban drainage systems. Therefore, it has become extremely difficult to separate river from the rest of the drainage system. Study of interaction between such river and urban drainage is necessary for urban drainage planning and design. Present study showcases how urban river modelling using InfoWorks Collection System (CS) on Berop River, Perak (Malaysia), can assist stormwater system design. Calibrated using historical flood event, the developed model was used for evaluation of various design storms, possible scenarios as well as existing and future landuse condition. The study found that within a data scarcity condition, InfoWorks CS played a significant role in providing good platform for stormwater system modelling as well as satisfactory simulations and analyses for complex combination of river and urban drainage stormwater system. This is the much needed advantage for practising engineers in time saving stormwater system design.
Urban Drainage Planning and Modelling - Hydraulic Performance
In this report the performance of the urban drainage system (UDS) of Fehraltorf is assessed by hydrodynamically simulating the waste water flows in the sewer pipes. The computation is done using the storm water management model for the catchment area over a time period of 30 years with rain data from Kloten (temporal resolution of 10 min). The rain data is verified whereas the actual model cannot be calibrated due to time restrictions. The UDS is insufficiently performing for one design storm event at eight manholes. Both the flooding and the backwater frequencies are examined at one critical area consisting of three manholes (565, 566 and 567). To reduce the current flooding frequencies (0.07-0.23 a-1) as well as the backwater frequencies (0.57-0.67 a-1) three mitigation measures are suggested: increasing the pipe diameters from 300 mm up to 500 mm or 800 mm respectively, or reducing the impervious areas from 26% down to 5%. The second strategy (800 mm pipes) shows the most promising results: no more flooding (0.00 a-1) and a backwater frequency of 0.03 a-1 for one manhole (0.00 a-1 for the others). The associated implementation costs are estimated to be approximately CHF 420’000. While the effects of climate change on the UDS are probably negligible, the population increase by 20-25% until 2040 is expected to have a significant impact. Therefore, running additional simulations considering different growth scenarios is suggested for all proposed strategies
2020
The recent alternation of urban hydrology is seen significant due to the growth of urban sprawl. In the changed urban hydrology and urban settings, the city drainage is seen underperformed and problems are manifolds. This study therefore aims to evaluate the hydrologic performance of drainage under different land use patterns demonstrating urbanization effects using the Mahesh Khal in Chattogram as a studied watershed. This study analyses land use pattern of the study area with the data collected through field investigation and also gathered from the secondary sources using ArcGIS 10.4. The change patterns are realized portraying scenarios with statistical significance. The study revealed that the trends of built-up area is significantly high figuring out over doubled in last 30 years period; 24% in 1998 to 53% in 2018 compromising the lost of open water and vegetative surfaces. In align with such changes, the peak discharges found for 2, 5, 10, 25, 50 and 100 years return period we...
Estimation of surface runoff potential of a watershed in semi-arid environment — A case study
Journal of the Indian Society of Remote Sensing, 2001
Jakarta is a capitol of Indonesia which is located at downstream part of Ciliwung river. Statistic shows that in 2015, there are more than 750,000 people living in Ciliwung watershed which cost the changes in land use and uncontrolled use of river banks for settlement and population activities. Increases of impervious area will be correlated with the surface runoff. The aim of this paper is to analyse the potential impact of land use change on the surface runoff at upper Ciliwung watershed using hydrological model HEC-GeoHMS. Initial condition of this model adopt the SCS-CN model that represent the Upper Ciliwung Watershed characteristic. Rainfall event on 3 February 2007, the highest rainfall in last decade, were analysed at this simulation. This event applied for different land use from 1990 until 2017, with land use change increase by 12% each year, a flood hazard analysis has been carried out and it showed that the area in highly peak flood increased by 30%.
ASSESSMENT OF STORM WATER RUNOFF WITH ARC-SWAT AND SWMM IN MYMENSINGH DISTRICT
ICACE-2018, 2018
Mymensingh District situated in flood plain between Old Brahmaputra and Banar river. Development of this area for accommodation purpose has some adverse effect to the environment as well as the water logging problem. The elevation of the area is increased above the high flood level of the Old Brahmaputra river to overcome the flooding problem. Besides some new cannel are constructed which has divided the area into small parts. In this study the catchment of Mymensingh District is delineated using ArcSWAT, which is an extension of ArcGIS and the Peak Runoff of the sub-catchment is determined using the model SWMM. First runoff coefficients have been chosen for different sub-catchment areas. The design rainfall values have been evaluated using Gumbel's distribution for return period of 5 years and 10 years. The value of rainfall for 5 years and 10 years return periods are 226.6mm/day and 286.91mm/day respectively. The ranges of peak runoff, slope and runoff coefficient for different sub-catchments are between 3.18m3 /s to 1038m3/s, 0.01 to 0.04 and 0.295 to 0.705 respectively. It is observed that the model simulated value is close enough to the manually calculated value. The peak runoff obtained from the model simulation for high intensity of rainfall is less enough the drainage discharge capacity of the channels. However, during monsoon the HFL of the surrounding rivers may be higher than the water level of the drainage channels. To overcome this problem pump station can be introduced in each outlet. INTRODUCTION Mymensingh is located on the bank of the Brahmaputra river, but the urban areas are not usually affected by regular flooding except the extreme events such as the floods of 1988. An extensive network of internal channels and water bodies is linked to the external river system to which the stormwater and urban wastewater drain. The planned area has two parts-the built up urban areas, and the presently rural areas which will be developed under the plan in future. The urban areas are regularly affected by internal stormwater flooding primarily due to inadequate drainage infrastructure, and deficiency in maintenance and management of the drainage system. Growth of urban areas in Bangladesh has profound influence on the performance of urban drainage systems. Experiences in other major urban areas show that several factors determine the effectiveness and efficiency of the system. The main objectives of this study with regard to the study area are-i) to estimate the maximum runoff for different sub catchments ii) to design of the drainage network and iii) to assess the drainage operation during flood period.