AP Environmental Science Quiz: Methods To Reduce Urban Runoff

What this quiz covers

This quiz focuses on Methods To Reduce Urban Runoff, giving you a quick way to practice the rules, question types, and explanations that matter most for AP Environmental Science.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

Question 1

1. Replace asphalt with permeable pavement that lets water pass into an underlying gravel layer and soil (correct answer)
2. Install taller curbs and add more storm drains to move water off streets faster
3. Line stormwater channels with concrete to prevent seepage and speed conveyance
4. Increase road crown (slope) so water runs off the roadway more efficiently

Explanation: Urban runoff occurs when rainwater flows over impervious surfaces like asphalt and concrete, unable to infiltrate into the ground, causing rapid water movement into storm drains and potential flooding. Permeable pavement (option A) directly reduces surface runoff volume by allowing water to pass through its porous structure into underlying gravel and soil layers where it can infiltrate naturally. This mimics the natural water cycle by letting rain soak in where it falls, reducing the total volume entering storm systems. In contrast, options B, C, and D all focus on moving water away faster through traditional drainage infrastructure, which doesn't reduce runoff volume but merely relocates it. Installing taller curbs and more drains (B), lining channels with concrete (C), and increasing road slope (D) all accelerate water movement but fail to address the root problem of excessive impervious surface area. By replacing asphalt with permeable materials, the city can significantly reduce both runoff volume and the frequency of combined sewer overflows during storms.

Question 2

1. Lower peak runoff and improved water quality due to filtration and settling (correct answer)
2. Higher peak runoff because vegetation increases overland flow
3. No change in runoff because only large dams can affect stormwater
4. More combined sewer overflows because less water infiltrates

Explanation: Urban runoff management through green infrastructure provides multiple environmental benefits beyond just flood control. The combination of bioswales, permeable surfaces, and retention ponds creates a treatment train that reduces both runoff volume and peak flows. During moderate storms, this system would likely produce lower peak runoff because water is temporarily stored and slowly released rather than quickly conveyed to drainage systems. Additionally, the biological and physical processes in these green infrastructure elements improve water quality by removing sediments, nutrients, and other pollutants through settling, filtration, and plant uptake.

Question 3

1. Convert parking stalls to permeable pavement (correct answer)
2. Add more storm drains to the lot
3. Increase asphalt thickness to reduce cracking
4. Install a concrete apron that directs water to the street faster

Explanation: Urban runoff management from large parking areas often requires multiple approaches to achieve significant volume reduction. While a retention pond provides important storage and peak flow control for runoff leaving the site, it doesn't reduce the volume of runoff generated on the parking lot itself. Converting parking surfaces to permeable pavement allows rainfall to infiltrate where it lands rather than becoming runoff, reducing the total volume that needs to be managed by the retention pond. This combination of source control and end-of-pipe management provides more comprehensive runoff reduction.

Question 4

1. Clay-rich soils with low permeability (correct answer)
2. Presence of native plants with deep roots
3. Use of mulch on the soil surface
4. Moderate slope directing runoff into the garden

Explanation: Urban runoff management through infiltration-based systems depends heavily on soil conditions and site characteristics. Rain gardens work best when water can infiltrate into the ground rather than ponding on the surface for extended periods. Clay-rich soils with low permeability prevent effective infiltration, causing water to remain on the surface and potentially creating mosquito breeding habitat or plant stress. Effective rain garden design requires proper soil assessment and may need soil amendments or underdrain systems in areas with poor natural drainage. Native plants, mulch, and moderate slopes all help improve rain garden performance.

Question 5

1. Green roofs (correct answer)
2. Retention pond
3. Conventional asphalt resurfacing
4. Concrete channelization

Explanation: Urban runoff management strategies work at different points in the water cycle and through different mechanisms. Green roofs intercept rainfall directly where it lands, preventing it from ever becoming surface runoff through retention in growing media and evapotranspiration by plants. Retention ponds and permeable pavement work primarily at ground level after water has already fallen. While all three are valuable components of comprehensive stormwater management, green roofs have the unique advantage of preventing runoff generation rather than just managing it after it forms.

Question 6

1. Install larger storm sewers to increase drainage capacity
2. Construct a concrete flume to move water quickly to the river
3. Add permeable walkways, rain gardens near parking areas, and a retention pond for overflow (correct answer)
4. Pave additional areas to prevent soil saturation and reduce standing water

Explanation: Urban runoff management has evolved from traditional "gray infrastructure" focused on rapid conveyance to "green infrastructure" that mimics natural hydrology through infiltration and storage. Option C best reflects a green infrastructure approach by combining multiple practices that work together to reduce runoff at its source: permeable walkways allow direct infiltration where people travel, rain gardens near parking areas capture and filter runoff from these impervious surfaces, and a retention pond provides overflow storage for larger storms while also improving water quality. This distributed approach manages water throughout the site rather than simply collecting and conveying it away. Options A and B represent traditional engineering solutions that increase drainage capacity and conveyance speed but don't reduce runoff volume or provide water quality benefits. Option D would actually worsen the problem by creating more impervious surface area. Green infrastructure recognizes stormwater as a resource to be managed on-site rather than a waste product to be disposed of quickly. By incorporating these natural systems into the sports complex design, the city can reduce downstream flooding, improve water quality, create aesthetic amenities, and potentially reduce long-term infrastructure maintenance costs.

Question 7

1. Green roof, because it reduces runoff by increasing stream channelization
2. Permeable pavement, because it allows rainfall to infiltrate through the courtyard surface (correct answer)
3. Green roof, because it prevents rainfall from occurring over the courtyard
4. Permeable pavement, because it increases impervious cover and speeds runoff

Explanation: Urban runoff problems require solutions that address water where it falls or flows. The courtyard generates runoff because its asphalt surface prevents infiltration, so the most direct solution is to modify that surface. Permeable pavement would allow rainfall on the courtyard to infiltrate through the surface rather than becoming runoff. While green roofs provide runoff reduction benefits, they wouldn't directly address water that falls on the courtyard itself. The key principle is matching the solution to the specific source of the runoff problem.

Question 8

1. Use permeable pavers for driveways and walkways instead of poured concrete (correct answer)
2. Install additional streetlights to improve nighttime visibility
3. Increase road width to reduce traffic congestion
4. Line roadside ditches with concrete to prevent erosion

Explanation: Urban runoff is generated when rainfall cannot infiltrate into the ground and instead flows over impervious surfaces. Permeable pavers allow water to pass through gaps between individual units and infiltrate into the underlying soil or gravel base, directly reducing the volume of surface runoff. This approach addresses runoff at its source by restoring some of the natural infiltration capacity that was lost when impervious materials were installed. Options B, C, and D either don't affect runoff generation or actually increase impervious surfaces, which would worsen runoff problems.

Question 9

1. Replace asphalt parking lots with permeable pavement that allows water to pass into an underlying gravel reservoir (correct answer)
2. Install taller curbs to prevent water from leaving streets and sidewalks
3. Straighten and concrete-line the nearby stream channel to move water away faster
4. Increase the number of storm drains to route runoff more quickly to the river

Explanation: Urban runoff occurs when rainfall flows over impervious surfaces like asphalt and concrete instead of infiltrating into the ground. Permeable pavement is a key runoff reduction method that allows water to pass through the surface into an underlying gravel reservoir where it can slowly infiltrate into the soil. This directly addresses the problem at its source by converting impervious surfaces to pervious ones. Options B, C, and D all focus on moving water away faster rather than reducing the volume of runoff generated, which doesn't address the core issue of peak stormwater flows and water quality degradation.

Question 10

1. More infiltration and less surface runoff reaching storm drains (correct answer)
2. Less infiltration because permeable pavement seals the soil
3. Higher peak discharge because rain gardens increase impervious cover
4. No change because storm drains control infiltration rates

Explanation: Urban runoff management through green infrastructure creates measurable differences in watershed hydrology compared to conventional development. Conventional asphalt and storm drain systems rapidly convey water to receiving waters with minimal infiltration or storage. Green infrastructure systems like permeable pavement and rain gardens promote infiltration, reducing the total volume of runoff reaching storm drains. Rain gardens also provide temporary storage that delays peak flows. These combined effects result in more water soaking into the ground and less surface runoff during typical storm events.

Question 11

1. Groundwater recharge will likely increase because more water infiltrates through permeable surfaces and bioretention soils (correct answer)
2. Groundwater recharge will decrease because permeable surfaces prevent infiltration
3. Groundwater recharge will become zero because all rainfall is stored permanently in rain gardens
4. Groundwater recharge will not change because infiltration only occurs in deserts

Explanation: Urban runoff management through infiltration-based systems can significantly affect groundwater recharge patterns. Conventional impervious surfaces prevent rainfall from infiltrating into the ground, reducing natural groundwater recharge. Permeable surfaces and bioretention systems restore some of this infiltration capacity by allowing water to soak through engineered materials and into underlying soils. Rain gardens with amended soils can actually enhance infiltration beyond natural rates by providing better drainage and soil structure. This increased infiltration helps restore the natural water balance and can help sustain groundwater supplies in urban areas.

Question 12

1. Option 2, because permeable pavement and rain gardens treat runoff close to the source through infiltration and storage (correct answer)
2. Option 1, because a pond increases the amount of impervious surface on the street
3. Option 1, because it speeds runoff to the river
4. Option 2, because it routes all runoff directly into storm sewers

Explanation: Urban runoff management is most effective when strategies are matched to the specific sources of runoff generation. Option 2 better matches the goal because it addresses runoff where it is generated—on the street and sidewalks themselves. Permeable pavement allows water to infiltrate rather than becoming runoff, while rain gardens capture any surface flow before it reaches storm drains. A retention pond in a nearby park (Option 1) provides valuable storage for runoff that has already been generated, but it doesn't reduce the volume of runoff created by the impervious street surfaces. Source control is generally more effective than end-of-pipe management for reducing total runoff volumes.

Question 13

1. Green roof
2. Rain garden (bioretention cell) (correct answer)
3. Detention tunnel that rapidly conveys water downstream
4. Concrete-lined swale designed to minimize infiltration

Explanation: Urban runoff from rooftops and other impervious surfaces can cause erosion and water quality problems when concentrated flows discharge onto compacted soils. A rain garden, also known as a bioretention cell (option B), is a shallow planted depression designed to capture and temporarily hold stormwater runoff while allowing it to slowly infiltrate into the ground. The engineered soil mix and mulch layer work together to filter pollutants, while native plants help with water uptake and evapotranspiration. This green infrastructure practice specifically addresses the school's problem by intercepting roof runoff before it can cause puddling and erosion on the lawn. While green roofs (A) also manage stormwater, they are installed on building rooftops, not at ground level where downspouts discharge. Detention tunnels (C) and concrete-lined swales (D) are designed to convey water rapidly away rather than promote infiltration, making them inappropriate for solving the erosion and puddling issues. The rain garden provides multiple benefits including reduced runoff volume, improved water quality, and enhanced aesthetics for the school campus.

Question 14

1. Higher peak runoff and shorter lag time to the stream
2. Lower peak runoff and longer lag time to the stream (correct answer)
3. No runoff at all because green infrastructure eliminates rainfall
4. Higher peak runoff because vegetation increases water speed

Explanation: Urban runoff is heavily influenced by the amount of impervious surface coverage and the availability of infiltration and storage. Impervious surfaces create higher peak runoff and shorter lag times because water moves quickly over smooth surfaces to storm drains. Green infrastructure like permeable pavement, rain gardens, and green roofs reduces peak runoff by providing infiltration and temporary storage, and increases lag time by slowing water movement through natural processes. This creates a more natural hydrograph that better matches pre-development conditions.

Question 15

1. They increase runoff speed and reduce contact with soil, preventing pollutant uptake
2. They promote infiltration, slow flow, and allow sediment and some nutrients to be retained or taken up by plants (correct answer)
3. They seal the soil surface to prevent groundwater contamination, increasing surface runoff
4. They work only by adding chlorine to stormwater to disinfect it before it reaches the stream

Explanation: Urban runoff from subdivisions can severely impact nearby streams through increased flow volumes and pollutant loads. Vegetated swales and rain gardens work together to reduce these impacts through multiple mechanisms. They promote infiltration by allowing water to soak into the ground, slow flow velocity through vegetation and gentle slopes, and allow sediment and nutrients to be retained in the soil or taken up by plants (B). This combination of physical filtration, biological uptake, and increased residence time improves water quality while reducing runoff volume. These features do not increase runoff speed (A), seal soil surfaces (C), or rely on chlorine addition (D). The vegetation and soil in these systems act as natural filters, removing pollutants through settling, adsorption, and biological processes before water reaches the retention pond and ultimately the stream.

Question 16

1. Green roofs on apartment buildings to increase evapotranspiration
2. A retention pond with controlled outlet structures (correct answer)
3. Replacing street trees with artificial turf to reduce maintenance
4. Straightening a stream channel to move stormwater away faster

Explanation: Urban runoff from impervious surfaces causes flooding when stormwater systems become overwhelmed by high peak flows during storms. A retention pond (option B) is specifically designed to capture and temporarily hold large volumes of stormwater, then release it slowly through controlled outlet structures, effectively reducing peak discharge rates to downstream areas. This temporary storage flattens the hydrograph, preventing the sudden surge of water that causes flooding. Green roofs (option A) help by increasing evapotranspiration but have limited capacity for large storm events. Option C (artificial turf) actually increases runoff by creating another impervious surface. Option D (stream straightening) accelerates flow and worsens downstream flooding. Among these choices, only the retention pond provides the substantial storage capacity and controlled release mechanism needed to significantly reduce peak flows.

Question 17

1. They increase runoff by creating a smoother surface that sheds rain faster
2. They reduce runoff by storing rainfall in the growing medium and returning some water to the atmosphere via evapotranspiration (correct answer)
3. They reduce runoff by chemically neutralizing acids in rainwater so it cannot flow downhill
4. They eliminate runoff by sealing the roof so no water can enter or leave

Explanation: Urban runoff occurs when impervious surfaces prevent rainfall from infiltrating into the ground, leading to increased surface flow. Green roofs reduce runoff by providing a growing medium that can absorb and temporarily store rainfall. The soil and vegetation on green roofs retain water like a sponge, and plants release water back to the atmosphere through evapotranspiration. This process both reduces the volume of water that becomes runoff and delays the timing of any water that does leave the roof. Green roofs essentially recreate some of the natural water cycle processes that are lost when buildings replace natural landscapes.

Question 18

1. It increases infiltration and temporary storage, reducing surface flow to storm drains (correct answer)
2. It increases imperviousness, causing faster drainage
3. It converts stormwater into potable water instantly
4. It redirects water to rooftops where it evaporates immediately

Explanation: Urban runoff is reduced when impervious surfaces are replaced with systems that promote infiltration and temporary storage. Permeable pavement with an underlying gravel reservoir works by allowing water to pass through the surface and temporarily storing it in the void spaces within the gravel. From there, water can slowly infiltrate into the underlying soil or be collected and discharged at controlled rates. This system reduces both the volume and peak rate of runoff by recreating some of the natural water storage and infiltration processes that existed before the area was paved.

Question 19

1. Add more storm sewer pipes to increase conveyance capacity
2. Build a rain garden (bioretention cell) planted with native vegetation in low-lying areas (correct answer)
3. Pave over remaining lawns to reduce muddy areas
4. Remove street trees to reduce leaf litter in drains

Explanation: Urban runoff increases when natural surfaces are replaced with impervious materials that prevent infiltration. Rain gardens, also called bioretention cells, are vegetated depressions designed to capture, store, and treat stormwater runoff. They reduce runoff through multiple mechanisms: temporary storage reduces peak flows, infiltration allows water to soak into the ground, and plants take up water through evapotranspiration. The engineered soil mix and native vegetation work together to both manage water quantity and improve quality by filtering pollutants. Options A, C, and D focus on moving water away rather than managing it through natural processes.

Question 20

1. Green roof that retains and evapotranspires rainfall (correct answer)
2. Increase roof slope to speed runoff to gutters
3. Connect downspouts directly to storm sewers to prevent puddles
4. Replace nearby trees with pavement to reduce leaf blockage

Explanation: Urban runoff management regulations increasingly require on-site stormwater management to reduce impacts on municipal drainage systems. When ground space is limited, green roofs provide an effective solution for managing rainfall on building rooftops. Green roof systems can be designed to retain the first several centimeters of rainfall through growing media storage and plant evapotranspiration. This approach meets regulatory requirements while providing additional benefits like building insulation and urban heat island reduction. The growing media acts like a sponge to absorb rainfall and release it gradually.