The Impact Of GI (Rainwater Harvesing) Towards A Sustainable Urbanism: Case Study
Green infrastructure (GI) has become an urgent necessity for societies that wants to upgrade their physical fabric to respond to the needs of citizens and be efficiently managed and maintained. It can positively contribute to liveable cities. This paper draws attention to how to integrate a rain water management plan for Green Infrastructure (GI) in neighbourhoods which has infrastructure problems mainly, rainwater floods and to what extent the use of GI guides will impact on the whole city. Furthermore, it demonstrates the experiences of different countries in this field and their sustainable solutions while taking into consideration the varying scales of local factors. The paper presents a case study of Smouha neighbourhood in Alexandria, Egypt which affected negatively by recently rainwater floods however; there weren't any applications of sustainable green infrastructure.
Liveable cities are largely determined by how efficiently their infrastructure are designed and integrated. Green infrastructure includes natural and semi-natural features which protect natural water cycle. Rain water management features could presents in some implementations such as street rain water harvesting, green roofs, green spacing and so on. When rain water management plan is integrated properly into the built environment, it provides social, economic and environmental benefits to enhance community liveability. Therefore, it must be considered at every level of city planning, architecture and land scape strategies.
Rethinking green infrastructure
Green infrastructure has a vital role in cities advancement which cannot be underestimated. The research includes the future strategies and implementations for rain water management towards GI development which can be applied in urban environments especially in developing countries to avoid more problems occur because of its poor infrastructure and to achieve GI effective services and benefits. Furthermore, "it is crucial to recognise that urban systems do not operate in isolation they interact. This therefore suggests that for resilience to be effective, the parties involved in each urban system also need to interact and work together. "
In city of San Diego they have followed an alternative method to redirect rainwater, they use a rain barrel to collect and store rain water. "In Berlin rainwater utilization systems were part of a large scale urban re-development. Rainwater falling on the rooftops of buildings is collected and stored in a rainwater basement tank, then used for toilet flushing, watering of green areas".
Water harvesting implementations
Harvesting rainwater could be an additional feature for a sustainable home water efficiency strategy. It could be utilized in homes for toilets, showers and could be properly filtered for drinking; on the other hand it could harvest to rain public gardens and for streets and parking's cleaning needs. It leads to a diversity of other practices that contributes to a greater sustainable environment. The research displays two implementations of rain water management which are street harvesting and cultivated surfaces harvesting. Those implementations positively affect the community development especially on the environmental sides.
Street water runoff which presents in rain water that falls directly on streets and pavements then flows down by gutters into the sewage. Water harvesting is the process of capturing and storing rainwater from streets then reuses it for irrigation, car wash and other potential uses. This process It treats rainwater as a resource and implements by using green gutters, rain water planters, rain water bump out and rain water trees trenches. Green gutter Rain water planter Rain water bump out Rain water trees tranchesFigure 2: street water harvesting features.
There are different types of permeable pavement allows water to pass through the surface, percolate through the existing subsoil and provides rain water storage media.
Cultivated Surfaces Harvesting
The term of cultivated surfaces is called for any planted area both on the rooftops of buildings which is called “green roof” or public green spaces such as planted gardens.
Green roof is a rooftop covered with a cultivated and vegetation plants; it involves high quality water proofing and drainage system. It also includes a root barrier, drainage and irrigation systems. Harvested rain water can be used to irrigate these crops on rooftops. There is enormous potential for harvesting roof rainwater, it can directly irrigate plants on green roofs or transfers by gutters to rain barrels or basement tank then collected and stored for other landscaping and cleaning use. "Huge range of large single storage tanks can be manufactured from plastic, metal or fibreglass, and range in size from 50 gallons to thousands of gallons. "
Green spaces and public gardens
Green spaces and gardens have a multitude of benefits and provide many services which have ecological, economic and social implications. Rain water harvested from streets and barrels can be utilized and managed to irrigate this planted spaces.
Environmenal impacts analysis of GI implementations
This section describes and examines the invaluable environmental impacts that can be achieved by using the GI implementations as follows:
- Reduces Rain Water Runoff Flow
- Increases City's Water Stock
- Reduces Energy consumption
- Improves Air Quality
- Improves Community Liveability
Environmental impacts of Streets Harvesting
Street harvesting reduces rain water runoff that minimizes the negative impacts and problems caused by rain full especially in developing countries which had a poor infrastructure. In the other side, this harvested water may be used in irrigation after treated and filtrate it that reduce the amount of potable water used residentially and increases water supply which is now a very important issue especially in Egypt. Water use requires energy to produce and transport, streets water harvesting may limits this energy required in only potable water and reduces energy use in irrigation, landscaping and wash purposes. As soon as it saves energy it may improve air quality and reduce atmospheric CO2.
Environmental impacts of Cultivated Surfaces Harvesting
"Green roofs can store significant amounts of water in their growing media. This water is eventually evaporated from the soil or transpired by the plants on the roof, thus reducing the runoff entering sewer systems and waterways". A green roof contains additional insulation and reduces solar radiation amount reaching the building's roof which can reduce a building’s energy use. In general, plants and cultivated surfaces absorbs atmospheric CO2, it filtrate and improves air quality. Trees in gardens and public green spaces provide shade; reduce wind speeds and provide a sense of place and well-being which may positively affects community liveability. The following matrix explains the relationship between implementation and environmental impacts which will affects, not affects or maybe affects.
Future vision to GI in Smouha neighbourhood
Smouha neighbourhood is a 400000-square meter, located in the center of Alexandria, overlooking the Sidi Gaber railway station and nearby El-Nozha international airport. It consists of residential areas and several activities of land uses. The data was gathered and observed by using the questionnaire form during survey in Smouha Neighbourhood. The results indicate that 74% of the residents suffer from many infrastructure problems as follows:-
- Frequent pressures due to its high density like most of the residential neighbourhoods in Alexandria.
- There are weakness in the sewerage network due to the pressure on water and electricity networks resulting from continuous new erection buildings, taking into consideration the built-up area equals to 75% from the over entire site.
- There is no integrated plan of rain water recycling or harvesting to the rainfall in the neighbourhood streets.
- Pavements, trees, green spaces aren’t designed to capture rainfall onsite, and green roofs are ignored.
Streets Harvesting in Smouha Neighbourhood
Direct and capture street rain water through pipes in storage tanks above or below ground to reuse it in irrigation of planting areas in Smouha's squares or charged into soil to increase water recharge.
Using rain water sewer and storage systems in main streets.
Replace permeable pavements instead of traditional one.
Using permeable paver in paths and buildings courts, permeable asphalt in main streets.
Cultivated services in Smouha Neighbourhood
Installing a green roofing system on the existing buildings will increase extra weight of the roofing system and determining capacity on the existing structure in addition to its high cost. Therefore, the installation of green roofs for new buildings must be taken into consideration, while encouraging residents to cultivate small plants in terraces or roofs on the existing buildings for the absence of green roofs.
Using the rainwater inlet for roof harvesting, where rainwater collects on roofs and terraces makes it way down a pipe then moved to suction tank where a filter is placed in the tank to clear the impurities of water. A fitted sensor in collection tank sends the water to the tank located on the terrace; water is then supplied to flats through the water storage tank which can be used for domestic purposes.
Green spaces and paths
- Enhance all roads that penetrate the residential zone by green paths connected to each other.
- Promoting the cultivation of various types of trees for several benefits.
- Create waking paths to allow pedestrian access through the existing super blocks development. Figure 8: Site plan (before & after).
Due to the energy crisis and environmental health disasters, initiating alternative means of transportation to the automobile is becoming increasingly emphasized in many cities and is likely to increase in the future. Green paths refer to a wide range and means of transport that reduces negative impacts. This is achieved by:
- Develop neighbourhoods that promote walking.
- Create direct routes to shorten walking distance.
- Design paths which emphasize bike’s safety and convenience.
Flooding, drought and lack of water stock are the most common world water problems which will fade by using rain water management plan. Rain water management for GI develops and enhances the community livability in the city. It has a lot of advantage on the social development because it increases green spaces, recreational areas and vegetation, in addition to its social, economic and environmental impacts. In the economic side rain water management saves money spend in solving rainfall problems, it also consider a free source for irrigation and other purposes. The environmental impacts which mentioned in this research will affect the public health and wellbeing towards a sustainable community.
The following recommendations are significant implications for the future of cities using green infrastructure:
- Countries are going through rapid urbanization should comprehend sustainable solutions to address its infrastructure.
- Provide effective rain water management plan which is cost effective in order to achieve economic growth.
- Integration of Green Infrastructure into existing and new urban communities: rainwater harvesting systems can improve or maintain watershed hydrology, reduce pollutant loading to receiving waters, increase water conservation, reduce stress on existing infrastructure, and reduce energy consumption.
- Decision-makers and stakeholders must encourage planners and designers of the vital role for applying green infrastructure guidance in the design of streets, landscape, open spaces and using green roofs in new buildings construction.
- Providing municipalities by Green Infrastructure guiding principles to be mentioned in the development of their integrated plans to assist significant economic development benefits.