Educational Displays for Schools
4. Building up the flood risk...
Rivers have always flooded after very heavy rain. Streets and buildings make things worse because rain cannot soak into the ground. Water pours off roofs, roads and pavements straight into the river. River levels rise very quickly, which can cause 'flash flooding'.
Notes for teachers
Urban development adds hard surfaces to the environment. These surfaces (roads, roofs, pavements, paved gardens) are not permeable so do not absorb water. Rainwater runs off quickly into storm drains which empty directly into river systems. This lack of absorbent surfaces in towns means rivers can rise rapidly after heavy rainfall.
- Investigate permeable and impermeable materials.
- Map a local area to show how much of the ground is permeable and how much is impermeable.