Planning for sustainability
You could say that the purpose of urban planning is to manage land use so that it is sustainable. This means it should bring economic benefits, with social equity and without causing environmental harm. The promotion of ‘socially and environmentally sustainable human settlements development’ is part of the mission of UN-Habitat, the United Nations programme that is ‘working towards a better urban future’ (UN-Habitat, n.d. 2). They set out five principles for urban planning, shown in Box 6.1 (UN-Habitat, n.d. 1).
Box 6.1 UN-Habitat’s five principles for sustainable neighbourhood planning
The UN-Habitat approach to urban planning is based on three key features of sustainable neighbourhoods and cities, which are that they should be compact, integrated and connected. Five principles support these three features:
- Adequate space for streets and an efficient street network.
- High density of people: at least 15,000 people per km2.
- Mixed land use: housing mixed with business and other economic uses.
- Social mix: houses in different price ranges and tenures (rented, owned etc.) in any given area.
- Limited land-use specialisation: large areas should not be allocated for a single function.
In contrast with the zoning approach, these five principles emphasise the need for mixed land use developments that integrate different functions of residential, commercial and business together. Ideally, urban plans should mix housing with employment opportunities and include schools, shops and health care facilities. An adequate street network will allow access for cars, public transport and service vehicles. Plans should also consider the need for space for places of worship and for entertainment and leisure. Incorporating this diverse range of requirements for the urban environment is challenging. To be successful and sustainable, urban plans should ideally be developed with the participation of the people who will be living and working in the area. Meeting these expectations also requires significant economic resources, an effective decision-making and regulatory framework, and good governance.
We will now consider in a little more detail some aspects of sustainable urban planning that are particularly relevant to WASH, the environment and health, but are typically absent from unplanned developments. These are: housing quality; the infrastructure related to water, sanitation and solid wastes management; drainage systems; and green spaces.
One of the key elements to address health problems in poor urban areas is the quality of housing construction. Houses must be built with materials that are waterproof and durable, using appropriate construction techniques and following correct procedures. Regulatory systems need to be in place to ensure that buildings are constructed to a specified standard and monitoring procedures should be established to ensure compliance. However, the affordability of housing also needs to be considered. A research study found that the majority of households in Addis Ababa were unable to afford to build dwellings that met the standards set in 1994 and 2003 (Bihon, n.d.).
Infrastructure for water, sanitation and solid waste management
If you were planning a new water supply system for a town the first thing you would need to consider would be the source of water. (Some aspects of water source selection were discussed in Study Session 4.) Key questions include: Will there be enough water to meet the needs of the people living in the town? Will there be enough to meet future demand, say for the next 10 or 20 years? Is the quality of water acceptable? What water treatment will be needed to ensure the water is safe to drink? How far is the source from the town? And how will the water be moved from the source to users? Answering these questions is a complex technical process requiring models and calculations based on the number of people using the supply, expected use for non-domestic purposes, future expansion and growth, and geographical and hydrological survey data. In addition, for a piped water supply system, the infrastructure plan would include details of the network of water mains that deliver water to the users, with the layout of pipes and pumps required to distribute water to the new buildings.
Planning for sanitation is frequently neglected in urban plans. Sanitation services often focus on providing latrines and toilets but they do not give adequate attention to what happens next and how the waste is disposed of. Where houses are provided with piped water supplies and have water-flushed toilets, the most appropriate solution is a network of sewers to collect and transport the wastewater to a sewage treatment works. This is obviously a major undertaking at significant financial cost. In the absence of sewers, septic tanks are commonly used. Septic tanks are underground tanks into which sewage is piped. The wastewater remains in the tank for long enough for the solids to settle out as sludge and the liquid part is discharged from the tank, usually into the surrounding soil. The size of septic tank required is determined by the number of people using it. In heavily-populated urban areas, septic tanks are not ideal because there is limited space to accommodate the size and number of tanks required.
Where septic tanks and pit latrines are used, they need to be accessible for emptying (Figure 6.5). Sludge builds up in the tanks and pits and has to be removed on a regular basis. Faecal sludge management is a neglected area of urban planning. It requires systems to be in place for emptying the pits and tanks and transporting the sludge to an appropriate treatment plant or disposal site, away from the inhabited areas.
Urban plans also need to consider solid waste management. All sorts of wastes are indiscriminately discarded in towns and cities from homes, businesses and industry. Establishing systems to collect and manage the waste is a significant challenge, but urban planners can contribute by ensuring that the streets they design are wide enough to accommodate collection vehicles and that sites are identified for waste handling and disposal.
Minimising the risk of flooding by designing effective drainage systems is another important aspect of urban plans. This is partly a matter of designing and building drains that are large enough to cope with high volumes of water. Rainwater from roofs can be collected and put to good use rather than just allowed to run into the drains. There are also ways of reducing the area of impermeable hard-surfacing so that more water can infiltrate into the ground and the speed and volume of surface run-off is reduced. These sustainable drainage systems (SuDS) include a range of techniques such as using gravel or cobblestones, which are permeable, rather than solid concrete, leaving grass or bare earth areas where possible so that water can infiltrate into the ground, and building ponds or water-holding areas into the drainage system so that rainwater is temporarily contained and the speed of flow is reduced.
Parks and other green spaces are important components of the urban environment for several reasons. Firstly, they are pleasant and enjoyable places to visit, offering a peaceful respite from busy city life (Figure 6.6). They provide areas of natural ground which absorb run-off and assist in the problems of surface water drainage. They also have a measurable cooling effect and can reduce the impact of the urban heat island. Feyisa et al. (2014) studied parks in Addis Ababa and found that the temperature inside the parks was as much as 6.7 ºC cooler than in the surrounding city.