AQA A-level Geography · 3.2.3

Urban drainage

50 exam-style questions with answers for 3.2.3 Urban drainage in AQA A-level Geography (spec 7037). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 3.2.3.5 · Urban hydrology
Explain how urbanisation changes the storage areas in a drainage basin. [4 marks]
Answer:
Interception is reduced because there is less vegetation to hold rainfall (1); surface storage falls as puddles and hollows are filled or paved over (1); soil moisture and groundwater storage decrease because impermeable surfaces prevent infiltration (1); water is moved quickly through drains and sewers instead of being stored (1).
Question 2 · Spec 3.2.3.5 · Urban hydrology
Explain how impermeable surfaces change the way water moves through an urban catchment. [4 marks]
Answer:
Roofs, roads and pavements prevent infiltration, so surface runoff increases (1); less water reaches the soil and groundwater, so baseflow decreases (1); evapotranspiration is lower because there are fewer plants and less open soil (1); rainfall reaches rivers faster, raising peak flow and flood risk (1).
Question 3 · Spec 3.2.3.5 · Urban hydrology
Explain how storm drains and channelised rivers affect flow in urban catchments. [3 marks]
Answer:
Storm drains carry water directly from roads and roofs to rivers (1); smooth channels and culverts reduce friction, so water travels faster (1); this shortens lag time and increases peak discharge downstream (1).
Question 4 · Spec 3.2.3.5 · Urban hydrology
Define lag time and explain why it is shorter in urban catchments. [3 marks]
Answer:
The time between peak rainfall and peak river discharge (1); impermeable surfaces make water run off quickly (1); drains and sewers carry water to rivers faster than natural flow paths (1).
Question 5 · Spec 3.2.3.5 · Urban hydrology
Describe the differences between an urban storm hydrograph and a rural storm hydrograph. [4 marks]
Answer:
The urban hydrograph has a steeper rising limb (1); a higher peak discharge (1); a shorter lag time (1); a steeper falling limb and lower baseflow (1).
Question 6 · Spec 3.2.3.5 · Urban hydrology
Define the following hydrograph terms: peak discharge, rising limb, falling limb and baseflow. [4 marks]
Answer:
Peak discharge is the highest river flow after a storm (1); the rising limb is the increase in discharge as the storm water reaches the river (1); the falling limb is the decline in discharge after the peak (1); baseflow is the normal flow supplied by groundwater (1).
Question 7 · Spec 3.2.3.5 · Urban hydrology
On a hydrograph, rainfall peaks at 10:00 and discharge peaks at 11:30. Calculate the lag time. [2 marks]
Answer:
11:30 minus 10:00 (1); 1.5 hours (1).
Question 8 · Spec 3.2.3.5 · Urban hydrology
A stream is 4 m wide and 0.5 m deep on average and its velocity is 1.5 m per second. Calculate the discharge in cubic metres per second (cumecs). [3 marks]
Answer:
Cross-sectional area = 4 × 0.5 = 2 m² (1); discharge = area × velocity (1); 2 × 1.5 = 3 cumecs (1).
Question 9 · Spec 3.2.3.5 · Urban hydrology
Peak discharge on a river rises from 20 cumecs before urbanisation to 45 cumecs after. Calculate the percentage increase. [2 marks]
Answer:
(45 − 20) ÷ 20 × 100 (1); 125% (1).
Question 10 · Spec 3.2.3.5 · Urban hydrology
Explain how rainfall characteristics influence the size of an urban flood. [3 marks]
Answer:
High-intensity rainfall exceeds the capacity of drains and infiltration (1); long-lasting rain fills storage and drains until they overflow (1); previous rainfall leaves saturated ground and full drains, so more water runs off (1).
Question 11 · Spec 3.2.3.5 · Urban hydrology
Explain how catchment characteristics other than urban surfaces affect flood risk. [3 marks]
Answer:
Steep slopes and a rounded catchment shape bring water to the river faster (1); impermeable rock and clay soils increase runoff (1); a high density of streams and drains speeds the movement of water (1).
Question 12 · Spec 3.2.3.5 · Urban water cycle
Describe the urban water cycle. [4 marks]
Answer:
Water is imported from reservoirs, rivers and groundwater by pipes (1); rainfall on built surfaces becomes runoff into drains and sewers (1); used water goes to treatment works and is returned to rivers or the sea (1); leakage from pipes, and less infiltration and evaporation than in natural areas, change the balance of the cycle (1).
Question 13 · Spec 3.2.3.5 · Urban water cycle
Explain why water supply networks in cities lose water. [2 marks]
Answer:
Old, damaged and corroded pipes leak (1); pressure changes and ground movement cause bursts, and in the UK around a quarter of treated water can be lost (1).
Question 14 · Spec 3.2.3.5 · Urban water cycle
Explain how urbanisation affects water quality in rivers. [4 marks]
Answer:
Runoff washes oil, heavy metals, rubber and litter from roads into rivers (1); fertilisers and pesticides from gardens and sewage overflows add nutrients, causing eutrophication (1); road salt in winter and industrial discharges add pollutants (1); warmer runoff from hot surfaces lowers oxygen levels in water (1).
Question 15 · Spec 3.2.3.5 · Urban water cycle
Explain what is meant by the first flush effect. [2 marks]
Answer:
The first runoff after a dry period washes accumulated pollutants from surfaces into drains (1); this gives a short but highly polluted pulse of water in rivers (1).
Question 16 · Spec 3.2.3.5 · Urban water cycle
Explain how combined sewer overflows cause pollution. [3 marks]
Answer:
In older cities, one pipe carries both rainwater and sewage (1); during heavy rain the system is overwhelmed, and untreated sewage and runoff are released into rivers through overflows (1); this causes pollution, harms wildlife and creates risks for people using the water (1).
Question 17 · Spec 3.2.3.5 · Urban water cycle
Describe the Thames Tideway Tunnel. [3 marks]
Answer:
A 25 km tunnel under the River Thames in London, completed in 2024 (1); it intercepts overflows from the Victorian combined sewer system and carries them to the treatment works at Beckton (1); it aims to reduce the sewage discharged into the Thames by most of the current amount (1).
Question 18 · Spec 3.2.3.5 · Urban water cycle
Describe the importance of Bazalgette's sewers in London. [2 marks]
Answer:
Joseph Bazalgette built a network of sewers in the 1860s and 1870s that carried sewage away from central London (1); it reduced cholera outbreaks, but the network was designed for a much smaller population and now overflows (1).
Question 19 · Spec 3.2.3.5 · Urban water cycle
Explain why groundwater levels can rise under post-industrial cities. [3 marks]
Answer:
Industries that once pumped large amounts of groundwater have closed (1); less abstraction allows the water table to recover (1); rising groundwater can flood basements and tunnels and damage foundations (1).
Question 20 · Spec 3.2.3.5 · Flooding issues
Explain why surface water flooding is becoming more common in UK cities. [3 marks]
Answer:
More building and paving of gardens and green space increases runoff (1); drains and sewers are old and cannot cope with intense rainfall (1); climate change is bringing heavier downpours, and more people are living in flood-risk areas (1).
Question 21 · Spec 3.2.3.5 · Flooding issues
Describe the causes and effects of flooding in Hull in June 2007. [3 marks]
Answer:
About a month of rain fell in a day and overwhelmed drains in a city built on low-lying ground (1); around 8,600 homes and over 1,000 businesses were flooded (1); many people were out of their homes for months, and insurance claims and costs were large (1).
Question 22 · Spec 3.2.3.5 · Flooding issues
Explain how urban development made flooding worse in Houston during Hurricane Harvey in 2017. [3 marks]
Answer:
Over a metre of rain fell in some places, in a few days (1); the city had grown rapidly, with large areas of concrete and the loss of wetlands and prairies that stored water (1); drains and bayous were overwhelmed, and tens of thousands of homes were flooded (1).
Question 23 · Spec 3.2.3.5 · Flooding issues
Explain the causes of the Mumbai floods of 2005. [3 marks]
Answer:
About 940 mm of rain fell in 24 hours on 26 July 2005, the heaviest on record (1); drains were blocked by rubbish and silt and poorly maintained, and the Mithi River was narrowed by building (1); informal settlements on floodplains, high tide and impermeable surfaces made the flooding worse, and over 1,000 people died (1).
Question 24 · Spec 3.2.3.5 · Flooding issues
Explain why Jakarta is at high risk of flooding. [3 marks]
Answer:
Parts of the city are sinking by many centimetres a year because of groundwater extraction (1); the city is low-lying with 13 rivers crossing it, and rainy-season rain is heavy (1); drains and canals are often blocked, and rapid development has covered the land with impermeable surfaces (1).
Question 25 · Spec 3.2.3.5 · Flooding issues
Explain how climate change could affect flood risk in urban areas. [3 marks]
Answer:
Warmer air holds more moisture, so downpours become more intense (1); rising sea levels increase tidal and coastal flood risk in low-lying cities (1); drainage systems designed for past climates may not cope with larger storms (1).
Question 26 · Spec 3.2.3.5 · Management
Describe the hard engineering approaches used to manage urban catchments. [4 marks]
Answer:
Any four from: channelising and straightening rivers to carry water away faster (1); culverts and larger storm drains and sewers (1); flood walls and embankments (1); storage reservoirs and flood relief channels (1); barriers such as the Thames Barrier (1); pumping stations (1).
Question 27 · Spec 3.2.3.5 · Management
Evaluate hard engineering as a way of managing urban flooding. [3 marks]
Answer:
It protects people and property effectively where it is well designed (1); it is expensive and may need regular maintenance (1); it can move the problem downstream and harm the habitats and appearance of rivers (1).
Question 28 · Spec 3.2.3.5 · SUDS
Define sustainable urban drainage systems (SUDS) and state their aims. [3 marks]
Answer:
Drainage that copies natural processes to manage rainfall where it falls (1); they aim to reduce runoff and the risk of flooding (1); they also improve water quality and provide benefits for wildlife and people (1).
Question 29 · Spec 3.2.3.5 · SUDS
Describe examples of sustainable urban drainage systems. [4 marks]
Answer:
Any four from: permeable paving that allows water to soak through (1); swales, which are grassy channels (1); detention basins and retention ponds that store water temporarily (1); green roofs and walls (1); rain gardens and soakaways (1); wetlands and infiltration trenches (1).
Question 30 · Spec 3.2.3.5 · SUDS
Explain how permeable paving reduces flood risk. [3 marks]
Answer:
It has gaps or a porous surface that allow water through (1); water is stored in the stone layer below, and infiltrates into the ground or flows slowly to a drain (1); this reduces surface runoff and peak flow, and traps some pollutants (1).
Question 31 · Spec 3.2.3.5 · SUDS
Explain how swales and detention basins manage urban runoff. [3 marks]
Answer:
Swales are shallow vegetated channels which slow the flow and allow infiltration (1); detention basins hold rainwater temporarily in a depression and release it slowly (1); both reduce peak discharge and filter pollutants, and can be used as green space (1).
Question 32 · Spec 3.2.3.5 · SUDS
Explain the advantages of SUDS over traditional drainage. [4 marks]
Answer:
They reduce flood risk by slowing runoff and increasing infiltration (1); they filter and improve water quality (1); they create green space, habitat and amenity and can cool the city (1); they can be cheaper to maintain than large pipes and are more adaptable to climate change (1).
Question 33 · Spec 3.2.3.5 · SUDS
Explain the limitations of SUDS. [3 marks]
Answer:
They need space, which is limited in dense urban areas (1); they do not work well on clay soils or steep or contaminated sites, and they may not cope with extreme storms (1); responsibility for maintenance can be unclear, and they can be hard to fit into existing urban areas (1).
Question 34 · Spec 3.2.3.5 · SUDS
Describe the sponge city programme in China. [3 marks]
Answer:
Launched in 2013–14, it aims to make cities absorb, store and reuse rainwater (1); measures include permeable pavements, green roofs, wetlands and parks that can flood (1); cities such as Wuhan and Shenzhen are pilot cities, but the scale of the programme and costs have led to mixed results (1).
Question 35 · Spec 3.2.3.5 · SUDS
Describe how Copenhagen has adapted to heavy rainfall. [3 marks]
Answer:
After severe cloudburst flooding in 2011, the city produced a Cloudburst Management Plan (1); it is creating green streets, parks and basins that can store water, and improved drains (1); the aim is to reduce flood damage and provide recreation space in everyday conditions (1).
Question 36 · Spec 3.2.3.5 · Catchment management
Explain how planning rules can reduce urban flood risk. [3 marks]
Answer:
Restricting building on floodplains keeps them free to store floodwater (1); requiring SUDS and limits on paving over gardens reduces runoff from new developments (1); the Flood and Water Management Act 2010 gave councils the responsibility for local flood risk (1).
Question 37 · Spec 3.2.3.5 · Catchment management
Explain how rainwater harvesting and greywater recycling contribute to sustainable water management. [3 marks]
Answer:
Rainwater collected from roofs can be used for toilets and gardens (1); greywater from baths and sinks can be treated and reused (1); both reduce demand for mains water and reduce pressure on drains (1).
Question 38 · Spec 3.2.3.5 · Catchment management
Explain why conflicts arise between stakeholders in managing urban catchments. [3 marks]
Answer:
Developers want to build on cheap land, which may be on floodplains (1); residents and conservation groups want to protect homes and habitats (1); councils and agencies have to balance cost, housing needs and long-term sustainability (1).
Question 39 · Spec 3.2.3.5 · Catchment management
Evaluate sustainable drainage compared with hard engineering approaches. [4 marks]
Answer:
Sustainable approaches work with natural processes and give extra benefits such as habitats and recreation (1); they are often cheaper and easier to adapt than large engineering schemes (1); hard engineering gives high levels of protection for dense, high-value areas (1); the best approach is often a mixture of both, depending on space and risk (1).
Question 40 · Spec 3.2.3.5 · River restoration
Define river restoration and explain why it is carried out in urban catchments. [3 marks]
Answer:
Returning a modified river to a more natural state (1); urban rivers have often been straightened, culverted or covered, which destroyed habitats and increased flood risk (1); restoration can improve water quality, wildlife and recreation (1).
Question 41 · Spec 3.2.3.5 · River restoration
Describe the reasons for the River Quaggy restoration in south east London. [3 marks]
Answer:
The river had been straightened and put into concrete channels and culverts (1); parts of Lewisham and Greenwich flooded in 1968 and again in 2000, damaging homes (1); the channel had little wildlife value and the area lacked open space (1).
Question 42 · Spec 3.2.3.5 · River restoration
Describe the aims of the Sutcliffe Park and Quaggy restoration. [2 marks]
Answer:
To reduce the flood risk to properties downstream (1); to create a natural wetland park with wildlife habitats and open space for local people (1).
Question 43 · Spec 3.2.3.5 · River restoration
Describe the attitudes and contributions of the parties involved in the River Quaggy project. [3 marks]
Answer:
The local campaign group, the Quaggy Waterways Action Group, pressed for action after repeated flooding (1); the Environment Agency and Greenwich Council planned and funded the scheme, and Thames Water also contributed (1); some residents and sports users were concerned about losing playing pitches and about the cost (1).
Question 44 · Spec 3.2.3.5 · River restoration
Describe the activities carried out during the Sutcliffe Park restoration. [3 marks]
Answer:
The concrete channel was removed and the river re-meandered through the park (1); a flood storage area was created, holding water during storms (1); wetlands and wildlife habitats, footpaths and a visitor area were added (1).
Question 45 · Spec 3.2.3.5 · River restoration
Evaluate the outcomes of the River Quaggy restoration project. [4 marks]
Answer:
Flood risk was reduced for hundreds of properties downstream (1); wetland habitats supported birds, invertebrates and plants and created a green space for the community (1); the park is popular and has won awards (1); however, the scheme was costly and only protects against floods up to a design standard (1).
Question 46 · Spec 3.2.3.5 · River restoration
Describe the reasons for and aims of the Cheonggyecheon restoration in Seoul. [3 marks]
Answer:
The stream had been covered with concrete from the 1950s and an elevated highway built above it, which became polluted and unsafe (1); the aim was to revive the city centre, improve the environment and reduce the heat island effect (1); the project also aimed to create a public space and boost tourism and business (1).
Question 47 · Spec 3.2.3.5 · River restoration
Describe the activities and outcomes of the Cheonggyecheon project. [4 marks]
Answer:
The highway and concrete cover were removed between 2003 and 2005, and a 5.8 km stream was reopened (1); water is pumped from the Han River to keep it flowing (1); temperatures along the stream are several degrees lower than nearby streets, and wildlife and visitor numbers rose (1); traffic changes and land values have changed the area, and the cost was high (1).
Question 48 · Spec 3.2.3.5 · River restoration
Describe the attitudes of different parties to the Cheonggyecheon project. [3 marks]
Answer:
The mayor and city government led the project as a symbol of a greener city (1); many shopkeepers and traders opposed it, fearing a loss of trade during construction (1); environmental groups and many citizens supported it, but some criticised the artificial nature of the stream and the costs (1).
Question 49 · Spec 3.2.3.5 · Evaluation
Assess the extent to which river restoration is a sustainable approach to managing urban catchments. [6 marks]
Answer:
Restoration works with natural processes, slows flow and stores floodwater (1); it improves water quality and creates habitats, increasing biodiversity (1); it provides green space that improves health and local property values (1); however, space is needed, which is limited in dense cities (1); schemes can be costly and may displace local land uses or people, as in the opposition of traders in Seoul (1); the long-term success depends on maintenance, funding and community support, and the project must deal with the pollution sources in the wider catchment (1).
Question 50 · Spec 3.2.3.5 · Urban hydrology
Describe how river velocity and discharge can be measured in the field to compare urban and rural streams. [3 marks]
Answer:
Time a floating object over a measured distance, or use a flow meter, and repeat to find the average velocity (1); measure the width and depth at intervals to find the cross-sectional area (1); calculate discharge as area multiplied by velocity and compare sites upstream and downstream of urban areas (1).

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