Teacher guide Permeable

Teacher guide Permeable pavements Flooding Floods happen when the soil can no longer absorb the water falling directly onto the ground or overflowing from a river, pond or dam. Instead of soaking into the soil, the water runs off. Too much runoff and you have a flood. When natural vegetation is replaced with an impervious surface, like concrete or brick, for example, the water cycle is altered – not only does water run off these surfaces, but the groundwater is not replenished. This can lead to more frequent flooding and lower water table levels. With an increasing population and, more importantly, an increasing urban population, more and more of us live surrounded by impervious surfaces. Coupled with more frequent and intense rainfall as a result of climate change, surface water flooding is an ever-growing risk. In this project, students will investigate the permeability of different surfaces and use their findings to design a permeable pavement or road. Prompts Porous vs. permeable. Porosity and permeability are both to do with how much and how easily water can flow through a space. Ask your students to find a definition for each. What are the differences? Do you want your pavement to be porous or permeable, or both? Why? You might like to set up your students with the following experiment method for testing permeability. Students will need to consider how to make the test fair (e.g. ensuring that the same volume of the material they are testing is placed in the bottle, using the same amount of water, pouring the water at the same rate, and so on), and how to measure their results (e.g. the amount of time it takes for a set volume of water to flow through the substance). • Cut the base off a plastic bottle. • Cover the mouth with a cheesecloth or similar material – something tightly woven enough to allow water through but not sand. • Fix the bottle to the edge of a table with the cheesecloth covered mouth at the bottom and the open base at the top. • On the floor underneath, place a measuring jug to catch the water, and place a tray on the floor under the bottle and jug to catch water splashes. • Fill the bottle with the substance you are testing. • Pour the water through. • Have paper towels and maybe a mop nearby to deal with any splashed water, which should be cleared up ASAP. 20

Student brief Permeable pavements Flooding (Physics, materials, flooding, climate change, environment) Have you ever wondered which type of soil is the most absorbent? Imagine you work for a company that designs pavements. You are hired to design the pavements for a new housing estate. The area already suffers from regular surface water flooding, so your client wants to make sure that the pavements do not further reduce the amount of land that can absorb rain water – they want a permeable pavement. Getting started Permeability is the degree to which liquids are able to flow through a material. Different substances have varying levels of permeability. Start by investigating the permeability of different types of soils, rocks and manmade materials (e.g. asphalt and concrete), either through research, or by designing and conducting an experiment. As well as being permeable, your pavement still needs to meet all the other design criteria that a pavement normally has. • What do people do on a pavement? Think about whether your pavement design can accommodate these activities. • How will your pavement hold up over time? • How will it fare in different weather conditions? Things to think about • How will you make sure your permeability experiment is fair? What variables will you need to control? • How many different types of materials will you test? You might also like to test out different mixes of materials (e.g. half sand/half clay), and some existing permeable paving solutions. • What other factors influence pavement design? Think about all the different ways people use pavements. Useful resources • First the heat, then the rain: The problem of surface water flooding in England https://theccc.org.uk/2018/07/30/first-the-heatthen-the-rain-the-problem-of-surface-waterflooding-in-england/ • Protecting property from flooding https://www.metoffice.gov.uk/weather/warningsand-advice/seasonal-advice/your-home/protectingyour-property-from-flooding • Evaluating the Infiltration Performance of Eight Dutch Permeable Pavements Using a New Full-Scale Infiltration Testing Method https://mdpi.com/2073-4441/6/7/2070/pdf • Evaluating the potential benefits of permeable pavement on the quantity and quality of stormwater runoff https://usgs.gov/science/evaluating-potentialbenefits-permeable-pavement-quantity-and-qualitystormwater-runoff?qt-science_center_objects=0#qtscience_center_objects Health and safety To avoid any accidents, make sure you stick to the following health and safety guidelines before getting started: • Find out if any of the materials, equipment or methods are hazardous using http://science.cleapss.org.uk/Resources/Student- Safety-Sheets/ to assess the risks. (Think about what could go wrong and how serious it might be.) • Decide what you need to do to reduce any risks (such as wearing personal protective equipment, knowing how to deal with emergencies and so on). • Make sure there is plenty of space to work. • Clear up slip or trip hazards promptly. • Make sure your teacher agrees with your plan and risk assessment. 21