Modelling the impacts of rainwater tanks on sanitary sewer overflows

Abstract

During the last six decades Kuwait City has experienced a rapid and unpreceded population growth with only a small increase in the respective urban area. This is largely due to the discovery of oil and arrival of thousands of new immigrants. The alarming rise in the urban density has caused issues for the residents' lifestyle, the economy and the environment. Historically, urban planning decisions in Kuwait were based on a series of “Master Plans” implemented by the government. Generally the plans, the last of which was formulated in 1997, promoted concentrated high density development in the city's Central Business District (CBD), and resulted into a low density urban sprawl expanding outwards in a radial fashion. A significant disadvantage of this top-down approach is the lack of inclusion of the citizens' suggestions and opinions, unlike similar expansion and planning policies in Western cities. Furthermore, the plans failed to incorporate measures to successfully accommodate the increase of vehicles and high traffic density, resulting into severe congestion issues and commuting times. Additionally, land development constraints set by the plans in combination with the increase of Kuwaiti citizens eligible to apply for housing welfare, caused a considerable increase of waiting times for receiving the government grants and drove property prices to levels out of reach for the majority of population. Pressure caused by these matters, has caused several protests in Kuwait, making the analysis of the impacts of current patterns of urban form expansion critical. To predict the future effects of the continuation of the existing pattern of urban growth in Kuwait on congestion and housing shortage a series of simulations based on Agent Based Modelling (ABM) and Geographical Information Systems (GIS) is proposed. ABM provides a mean to evaluate decisions by different citizen groups on their settlement patterns and interactions with other groups, such as the developers and the government. The simulations are able to receive and overlay GIS data inputs related to land use, transport networks, and demographics. The simulations have a horizon of 35 years (up to 2050). This paper discusses the rationale, design methodology and parameterisation of the ABM and the agent groups that constitute the framework. The base set of rules governing the behaviour of the agent groups was derived after analysing real data from historical Kuwait archives. The analysis findings are outlined in this paper. The findings imply that there are significant inherent correlations between urban form expansion and urban transportation quality as well as land use distribution. Using the historical trends as a guide for future expansion and assuming linear development along the current transportation networks it is possible to obtain five yearly predictions for the future state of: • Land use and development ratio • Accessibility to transportation networks, work, shopping centres, services and infrastructure • Population growth, distribution patterns and density. The analysis of the simulation outputs will enable the generation of a set of predictions for the impacts on congestion and housing shortage in Kuwait. The outputs of the model will also enable the evaluation of the centroid urban form expansion and can form a basis for reference for developing alternative urban planning and expansion policies not just in Kuwait, but in other modern cities especially ones that experienced rapid radial growth around their CBD. The proposed model with appropriate modifications will also be applied for simulating two alternative scenarios of urban form expansion in Kuwait in future work, hence allowing a quantitative comparison of urban planning strategies.