Bioelogical Drainage System (BIOECODS) for Effective Stormwater Control in the Tropics
This thesis attempts to explore alternative solutions to the conventional drainage system which has now been realized that the drastic discharge of rainwater resulted in significant ecological damage. The detrimental effects mainly concern the reduction in the natural ground water recharge, the increase in flood discharge and the considerable pollution of surface water. Since these disadvantages resulted in high costs for subsequent remedial measures (flood control, etc) widely applicable alternatives were needed.
This thesis outlines the national approach to stormwater management in Malaysia, and evolving implementation practices by State and Local government authorities. In response to the needs for paradigm shift the way the stormwater is managed, the Malaysian Government has introduced a new approach of planning and design of urban areas through the New Stormwater Management Manual for Malaysia (MSMA) that offers a sustainable solution for integrating the land development and urban water cycle. The research focused on new concepts for the urban stormwater runoff and the water quality management based on integrated stormwater solutions. The USM Engineering campus is a pilot project for urban stormwater management strategy as an example of an ecologically sustainable development based approach to urban stormwater management. The concept is based on open and natural drainage systems integrated into multipurpose open space/environmental corridors or greenways, is the most promising approach in newly developing or urbanizing areas.
This thesis aims to introduce such an alternative - the "Principle of Control-at-Source" based on Storage-Oriented Approach. With respect to its technical implementation the term "Bio-Ecological Drainage Systems”), further in this text referred to BIOECODS) has prevailed. The BIOECODS combines four engineering techniques to manage stormwater based on “Control-at-Source” approach namely infiltration, storage, conveyance and treatment by integrating the drainage components (i.e. ecological swales, on-line sub-surface detentions, and dry ponds) with the ecological pond components (i.e. detention pond, constructed wetland, wading stream and recreational pond). In combination, this approach increases runoff lag time, increase opportunities for pollutant removal through settling and bio-filtration, and reduce the rate and volume of runoff through enhanced infiltration opportunities. With this new approach, the main bulk of stormwater is collected and stored at its source to allow natural cleaning to occur prior to infiltration or controlled release to watercourses to reduce impact on river capacity.
Bio-Ecological Drainage System (BIOECODS) is an example of an innovative sustainable urban drainage system consists of different stormwater drainage facilities suggested in MSMA that designed to restore the natural environment implemented at USM's Engineering Campus with the following objectives:
• Promotion of stormwater infiltration from impermeable areas (e.g. roof tops, car parks) by using bio-ecological swales
• Gradual release of stormwater through the use of bio-ecological swales, on-line underground bio-ecological detention storages and bio-ecological dry ponds
• Treatment of stormwater quality using treatment train concept by utilising bio-ecological swales and bio-ecological ponds (e.g. wet pond, wetland) as the storm water moves downstream.
This thesis first introduces the survey study on the current stormwater management practices in Malaysia. The preliminary study has shown that the Urban Stormwater Management Manual (MSMA) was written based on overseas experience with limited local data and information of local conditions. In order to understand the current stormwater management practices in Malaysia and the deficiencies and errors in the MSMA manual, the surveys were conducted in order to evaluate the status of the stormwater management practices in Malaysia such as issues on public awareness, design aspect, best tools of stormwater facilities, errors or deficiencies in MSMA manual, cost, maintenance and public acceptance towards the MSMA manual.
In order to understand the behaviour of on-site source control facilities, this thesis also investigated the small scale pilot project of subsurface infiltration and storage tank system (on-site retention/detention system) to control stormwater quantity in Engineering Campus Universiti Sains Malaysia, Tronoh, Perak. The objective of the project is to implement the on-site source control and distributed storage systems to attenuate the peak flood hydrograph and volume by using three different infiltration and storage techniques namely module infiltration system, loose rock infiltration system and module storage tank system. The results were used as basis for the development of full scale pilot project of BIOECODS.
The basic principles of the design and concept of BIOECODS are discussed in detail in this thesis followed by a description of technical and constructions of BIOECODS. The objectives of the study for BIOECODS are focused on the hydraulic performance, water quality treatment train performance and the economic evaluation. In order to study the effectiveness of the full scale pilot project BIOECODS in treating the stormwater runoff, a storm water quality monitoring programme is being carried out by two methods namely grab sampling and automatic sampling method at ten sampling stations along ecological swales and at eight sampling stations along ECOPOND. The hydraulic performance of the BIOECODS system is focused on the ecological swale, dry pond and ecological pond. The effectiveness of an ecological swale is considered from the aspect of quantity control in terms of peak flow attenuation. The operational functional of a dry pond is calculated in terms of its capability to retain and drain the storm water. Dry pond is an off-line storage designed with the function to reduce peak discharge at the downstream by infiltrating through the layer of topsoil and river sand into the storage module underneath before flowing to the downstream of the sub-surface module of the swale. In addition, the Storm Water Management Model (XP-SWMM) is used to model and simulate the hydrologic and hydraulic performance of BIOECODS. Finally, the economic aspect of BIOECODS is studied by developing a simple method to conduct life cycle cost (LCC) analysis of BIOECODS. The simple LCC method was applied to a pilot project of USM Engineering Campus and it is found that the BIOECODS method has a lower capital cost but due to higher maintenance cost, its life cycle cost is little higher than the traditional method. However, the study has shown that the little increase in life cycle cost associated with the BIOECODS method can be balanced with the long term benefits gained from this innovative urban drainage system as part of sustainable approach in the new development area.
Overall, the outputs of this thesis give a useful insight into the status of stormwater management practices and effectiveness in Malaysia that will help with the development and delivery of new updated version of MSMA manual. Moreover, the results obtained from small scale project for on-site retention/detention systems and full scale project for BIOECODS have confirmed the good performance of the systems in attenuating the peak runoff and treating the stormwater runoff. Finally, the results can be used to support the MSMA manual with a local data for the updated version of MSMA manual in the next five years.
Effective new concept of Stormwater Management Manual for Malaysia (MSMA) is not easy to achieve and requires an innovative approach and commitments from all the key stakeholders. Furthermore, developing technologies or new approaches of stormwater management to improve the environmental protection and enhancement will always lead to temporary spatial and procedural inconsistencies. These issues can be seen as areas for development: addressing them allows the overall approach to be improved. It is only by methodically evaluating progress and barriers, and strengths and weaknesses at the grass roots level that these valuable lessons can be learnt and shared for the benefits of the nation.