Unit 1 - Essays - Storm Hydrograph SIMPLE ENGLISH UPDATED Flashcards
‘Urbanisation always results in an increase in channel flow.’ With the aid of examples, how far do you agree?
Paragraph 1: More Hard Surfaces Mean More Water Flowing into Rivers
Main Point: Cities have lots of hard surfaces, like roads and buildings, which don’t absorb water. This makes rainwater run quickly into drains and rivers.
Explanation: In natural areas, rainwater soaks into the ground, but in cities, it runs off hard surfaces straight into rivers, increasing channel flow.
Examples:
London: As London built more roads and buildings between 1990 and 2010, surface runoff increased by 15%, causing the River Thames to carry more water.
Mumbai: Over 75% of Mumbai is covered by hard surfaces, which leads to frequent flooding because water flows into rivers very quickly.
Different Places (Spatial): This problem is worse in big, crowded cities like Mumbai than in smaller towns with more parks and green spaces.
Over Time (Temporal): As cities keep growing, the amount of hard surfaces also grows, making this problem worse over time.
Extra Detail: Explain that more water flowing quickly means rivers fill up faster, increasing the risk of floods.
Paragraph 2: Faster River Flow Due to Straightened and Concrete Channels
Main Point: Cities often straighten and cover riverbanks with concrete to stop floods. This is called channelisation.
Explanation: While this can stop local flooding, it makes water move faster through the river, increasing channel flow downstream.
Examples:
Los Angeles River: Covered in concrete, which makes water flow much faster, causing bigger floods further down the river.
Sheffield, UK: Straightened parts of the River Don increased the speed of water flow by 20% during storms.
Different Places (Spatial): Older cities with more concrete rivers have this problem more than newer cities with natural rivers.
Over Time (Temporal): Once rivers are covered in concrete, this faster flow problem lasts for many years.
Extra Detail: Explain how fast water can carry more soil and rocks, causing problems like blocked river mouths and polluted water.
Paragraph 3: Less Water Flow Due to Water Extraction and Diversion
Main Point: Urban areas need a lot of water for homes, factories, and electricity, which reduces the amount of water in rivers.
Explanation: Cities take water directly from rivers and also build dams and tunnels that change where water goes, reducing channel flow.
Examples:
Las Vegas: Takes about 500 million gallons of water daily from the Colorado River, reducing how much water flows downstream.
Hoover Dam: Cuts down the Colorado River’s flow by 20% because it stores so much water.
Thames Tideway Tunnel (London): Moves stormwater straight to the sea, bypassing natural rivers.
Different Places (Spatial): Cities in dry areas, like Las Vegas, need to take even more water, making the problem worse.
Over Time (Temporal): The amount of water taken can go up during dry seasons or droughts, making rivers even smaller.
Extra Detail: Explain how less water in rivers can harm fish and plants that depend on steady water levels.
Paragraph 4: How Sustainable Urban Drainage Systems (SUDS) Can Help
Main Point: Many cities now use special systems called SUDS to manage rainwater better and reduce fast flow into rivers.
Explanation: SUDS include things like:
Permeable Pavements: Let rain soak through instead of running off.
Green Roofs: Plants on rooftops absorb rainwater.
Retention Basins: Hold back water to release it slowly.
Examples:
Copenhagen: Using SUDS has cut down fast water flows into rivers by 25% during heavy rain.
Green Roofs: Popular in cities like Berlin to reduce runoff by soaking up rainwater.
Different Places (Spatial): SUDS work best in new parts of cities that are built with them from the start.
Over Time (Temporal): If cities keep maintaining SUDS, they can help control water flow for many years.
Extra Detail: Explain how SUDS can also filter out dirt and chemicals from rainwater, making it cleaner when it reaches rivers.
Conclusion
Summary: Urbanisation often increases the speed and amount of water flowing into rivers because of hard surfaces and concrete riverbanks. However, water use and SUDS can reduce this effect.
Final Judgement: Overall, urbanisation usually leads to more water flowing quickly into rivers, but the impact can be controlled if cities plan carefully and use things like SUDS.
Final Thought: Cities need to balance building new roads and buildings with green solutions like SUDS to protect rivers and reduce flood risks.
