- Urban areas are covered in impermeable materials. Many urban structures are designed to shedwater quickly.
- This means that infiltrationis low in urban areas, so replenishment of groundwater stores is slow. Groundwater feeds rivers, so during drier periods, river discharge in urban areas is
- Precipitationis higher in urban areas than in rural areas, and storms are more intense – this increases surface runoff.
- Runoffis channelled through man-made pipes, which transports water to rivers and streams.
- Low infiltration rate, high surface runoffand channelling of water means that water enters rivers quickly. This gives a short lag time and high peak discharge, with a fast return to base flow.
- Catchment managementis a way of managing rivers and improving drainage systems by looking at the whole river catchment, and the interactions between water and land.
- It aims to minimise issues, such as flooding, drought, water pollutionand erosion in sensitive areas, and to improve river ecosystems.
Methods to Manage River Catchments
- Hard engineeringwhich involves man-made structures, such as dams, floodwalls and reservoirs, which are often used to prevent flooding and ensure a constant water supply.
- However, hard engineering schemes are often expensiveand can disrupt natural systems and they can also alter wildlife
- Soft engineeringwhich uses knowledge of the river basin and its processes to try to work with nature.
- It involves land use management. It can also involve river restorationand
- It is generally cheaperthan hard engineering, and it can improve the local environment.
- Conversely, planning restrictionscan limit the construction of new homes and businesses, and land use management is hard in areas that are already urbanised.
- Decisions about what methods to use are made by expertsin water management rather than residents, what is best for the catchment as a whole may not be best for all individuals, so some residents and communities may feel
- Catchment management schemes can also be
- Sustainable Urban Drainage Systems(SUDS) aim to imitate natural drainage systems, rather than channelling water through pipes and drains.
- They use several methods to decrease flooding, water pollutionand drought in urban areas:
- Vegetated trenchesincrease interception of rainfall, and retention basins store water.
- They help to increase infiltration and water storage which decreases runoff and channel flow,which lowers flood risk.
- Increased infiltration also decreases the amount of pollutantsentering watercourses.
- Vegetated roofsintercept rainfall and increase evapotranspiration, which reduces flood risk.
- Containerson the roofs of buildings catch and store rainwater for reuse. This helps to reduce drought risk.
- SUDS are more sustainablethan traditional urban drainage methods because they work with the natural environment to improve drainage and water quality.
- Vegetated trenches and roofs also provide new habitatsand increase
Restoring Water System – Enfield
- River restorationand conservation aims to restore river systems to a more natural It can help to reduce flood risk, decrease water pollution, create new habitats and increase biodiversity.
- One area that is restoring its rivers is Enfield,north London. Enfield has had regular floods.
- The area is heavily urbanised which has caused problemsfor drainage and water quality, including:
- The spread of urban structures has increased surface runoffand channel flow. This has increased the frequency and intensity of floods, over 9,000 homes in Enfield are at risk of flooding.
- Surface runoff from roads has increased levels of pollutants,such as oil and heavy metals in watercourses.
- Water pollution also comes from domestic sourceswhich is up to 10% of houses in Enfield have wastewater pipes that feed directly into rivers.
- In 2012, a project began to restorerivers in the area, with the following aims:
- Reduce flood riskand limit the impacts of flooding on habitats and residential areas.
- Reduce surface runofffrom roads and pollutants entering rivers in order to improve water quality.
- Provide more habitatsfor wildlife and new recreational areas for residents.
- The project has used SUDSto help restore river systems and meet these aims, for example:
- Vegetated trencheshave been created around roads to absorb runoff and decrease flood risk.
- Rain plantershave been installed in schools as this collects rainwater and manage the flow of water into drains, lowering flood risk.
- This also provided opportunities to educatechildren about water management.
- Wetlandshave been constructed to improve water quality.
- Lots of groupshave been involved in the project, for example:
- Defraand Thames Water are providing In 2012, Defra granted £340,000 to the project to construct more SUDS.
- Local resident’s reactions have been very positive. Volunteers have been involved in water quality monitoringand litter pickups.
- Local schoolssuch as Thames21 offers education sessions for local schools to increase engagement. In 2015, 1,000 students were involved in litter picking and wildlife monitoring.
- The project is ongoing, but it’s had some successesalready:
- Flood riskseems to be
- SUDS have reduced ammonialevels in Salmons Brook by 67% and nitrogen levels by 43%.
- Populations of eelsand some species of insects have increased.
- However, pollutionand litter are still an issue in many rivers.
Three Primary Sources of Waste
- Industrial waste- any waste that has been produced in the manufacturing process or from industrial activity.
- Commercial waste- any waste that is produced by
- Personal waste – any waste produced by private homes.
- Globally, the largest components of waste are organic material(46%), paper (17%), plastic (10%) and glass (5%). The majority of waste is easy to manage, but some materials
- A waste streamis the flow of waste from its origin through to its eventual disposal:
- Some products can be
- Others need to be broken downinto their component parts and each part disposed of