Zorkeflee Abu Hasan
The project consists of five volumes as stated below:
Volume I: Executive Summary
Volume II: Introduction & Data Collection
Volume III: Hydrological & Hydraulic Analyses
Volume IV: Water Quality Assessment
Volume V: Stormwater Master Plan
The Stormwater Management and Drainage Master Plan Study for the Town of Tanah Merah, Kelantan, is a master plan study initiated by the Department of Irrigation and Drainage (DID) Malaysia. The master plan aims to address stormwater related issues and problems in Tanah Merah town area. This study also covers the immediate surrounding areas set to undergo land use transformation from agriculture to commercial and industrial area as planned in the District’s Local Plan and State’s Structure Plan.
The objective of the study is as follows:
- To formulate the long term solution for the flooding, drainage and stormwater management problems in the existing built-up areas in order to reduce the adverse effects of flooding on people and property and to protect the existing and proposed development by implementation of an integrated stormwater management plan by providing an appropriate level of flood protection to community expectations.
- To optimise the effectiveness of the existing stormwater infrastructure network within the study area taking into account environmental effects and public expectations.
- To control the excessive sediment in watercourses to acceptable levels through the use of wetlands, green buffer zones and other sediment control measures.
- To collect and convey stormwater from a catchment to its receiving water with minimal impact by managing and improving the quality of stormwater runoff from urbanized catchment and its pollution loads in order to reduce the adverse effects of non-point source contamination of the receiving water environment.
- To optimise cost-effectiveness of new plan by incorporating rainwater harvesting strategies where appropriate to attenuate peak from subcatchment runoff and hence avoid the need for costly measures to widen channel sections and replace bridges or utilities.
- To protect and enhance the natural water-dependent ecosystems and enhance community access to and enjoyment of water courses environments and to protect and maintain river environments to a high environmental and aesthetic quality while promoting sustainable recreational opportunities, community health, aesthetics amenity and healthy environment.
Study Area and Problem Statement:
Tanah Merah town is located in District of Tanah Merah with a total catchment of 64 km square. It is the second largest town in State of Kelantan with rapid growth of development. The town is situated on the west bank of Kelantan River with the railway line run across the middle of the town.
Parts of the town area especially at the north and east where vast of the areas have been developed for the housing project was the ex-paddy field with a lowland topography. With the lack of the proper drainage system connecting the affected area and insufficient in density, these areas have been flooded during the heavy rainstorm. The situation has been even worst during the monsoon where the overflow from the Sungai Kelantan will backflow into the lowland areas through the existing Sungai Kepat, Sungai Tualang Bah, Sungai Maka and Sungai Alor Pechong which are lying at the side of Bandar Tanah Merah.
Future development is also expected increase imperviousness of the catchment. A part from disturbing hydrology, under designed drainage will also causes flash flood. Worse still, urbanization brings even more pollution issue to the area, which already has poor water quality due to lack of control.
Therefore, REDAC (Through USAINS Holdings Sdn Bhd, Corporate wing of Universiti Sains Malaysia) was appointed by DID to produce a drainage and stormwater management master plan for the area of town Tanah Merah to address these stormwater issues.
|Condition of Sungai Maka during flooding (right) and normal condition (left)|
Scope of Works:
In order to produce a comprehensive drainage master plan, the team had performed a series of research works, which include:
- Perform Data and Information Collection
- Conduct Topographical and Engineering Survey Supervisions as well as Geotechnical Investigations
- Conduct Site Investigations and Field Inspections
- Perform Analyses of Existing Conditions
- Identify Stormwater Issues and Problems
- Formulate Stormwater Management Alternatives
- Compare Alternatives and Select Recommended Plan
- Development of Stormwater Management Master Plan
- Produce Estimated Cost
- Prepare Implementation Plan
The procedure of work was made up of 3 general phases, data collection, analyses, as well as design and planning. The study kicked off with data collection process to gather all relevant information and data required for analyses. Data Collection can be divided into desk work and field works. Desk work includes gathering of all published data including rainfall and stream flow records, Light Detection and Ranging (LiDAR) data, land use maps, satellite images, and soil data.
Related reports and studies are also reviewed, including the existing municipal Local Plans, flood reports, and as built drawings.
The study team carried out a series of field works to complement data collection. These field works provided additional data to those collected through desk work. These field works includes:
- Stormwater Asset Inventory
- Water Quality Monitoring and Sampling
- Geotechnical Investigation
- Ground Water Monitoring and
- Engineering Survey Supervision
Geotechnical Investigation Work
Stormwater analyses were carried out to quantitatively identify the severity of stormwater related issues in Tanah Merah. Stormwater analyses include:
- Stormwater system modelling
An integrated hydrological and hydraulic model was applied to perform analyses on Tanah Merah. InfoWorks CS was used to establish the hydrological and hydraulic model. After calibration process against the December 2007 flood, the model was used to simulate various conditions including future catchment land use, various design storms and boundary conditions.
The simulations confirmed that Tanah Merah is heavily affected by water levels and flood from Sungai Kelantan. Flood water travel up Sungai Kepat and Sungai Maka and inundate many areas (many of which are inhabited) within the town. The existing urban drain network is poorly managed, under-designed and would definitely fail to cope with future runoff increase.
The apparent effect of urbanization
(a) Sungai Maka Longitudinal water profile for 10 year ARI event without Sungai Kelantan tailwater
(b) Sungai Maka Longitudinal water profile for 10 year ARI event coinciding with Sungai Kelantan 5 year ARI water level.
Apparent effect of Sungai Kelantan influence
Flood extent for 10 year ARI catchment coincide with 50 year ARI Sungai Kelantan event
- Water Quality Assessment
Water Quality assessment was carried out through site and laboratory testing to determine chemical parameters of water in Tanah Merah. From 25 sampling sites, sample water was tested for 11 water quality parameters from the simplest pH measurement to Total Coliform determination. It was found that water quality in Tanah Merah is generally poor with high ammoniacal nitrogen, bio-chemical oxygen demand, oil and grease as well as total coliform count due to the lack of proper sewage treatment system in the town.
Stormwater Master Plan:
After identifying issues and considering design constraints, the study team proposed a stormwater management master plan consisting of two parts namely the structural stormwater master plan and non-structural stormwater management plan. Both parts will play equally important role to manage stormwater in Tanah Merah at long term sustainably.
Structural Master Plan
The proposed structural master plan consisted of all physical modification and upgrades deemed necessary to improve stormwater management in Tanah Merah by the study team. The structural upgrades are designed based on two important design criteria, which is to provide sufficient flood protection and to provide runoff control in terms of water quantity and quality. Among the promoted upgrade includes:
- Waterway Upgrades
- Gate & Control structures
- Flood Detention Ponds
- Stormwater Detention Facilities
Non-structural Stormwater Management Plan
Non-structural stormwater management plan was tailored to complement the structural master plan to enhance stormwater management in Tanah Merah. This plan consists of several components to provide management suggestions to the local authorities in stormwater management. Non-structural measures included were:
- Urban/ Development Planning
- Low Impact Development
- Operation and Maintenance
- Public Outreach and Education
- Flood Management Plan