Engineers consider constraints (limitations) when building a community. These constraints might include the material and time requirements of building up the community, as well as the social, ethical and environmental considerations that are imposed by the building up of the community. As with most large projects, knowledge comes with experience. Engineers building up the community of Chicago did not have the experience they have now in knowing the effects of large communities of paved areas (which leave little land exposed to soak up rainwater). If those engineers had known then that this would become a problem, they might have planned scattered parks and areas with permeable surfaces to "soak up" the storm water. However, since the city was already designed and built as it is today, engineers are working to improve that situation by designing and maintaining a very expensive system for managing storm water underground to prevent floods. Student are introduced to rivers, and to the components of the water cycle. They think about the effects of communities, sidewalks and roads on the natural flow of rainwater. Students also learn about the role of engineering in community planning and protecting our natural resources. Who can tell me what a river is? Yes, a river is a part of the land that has water flowing in it at least some time of the year. Land, called banks, surrounds each side of a river. We also call this area the riparian zone, which just means the land on either side of the river. Who has ever seen a river? Is there one near our school or your home? What might be found in the riparian area of the river? (Possible answers: Plants, animals, insects, sand, gravel, bike path, bridge, sidewalks, etc.) For what purpose might we use a river? (Accept all reasonable answers, which might include: fishing, transportation, swimming, kayaking, drinking water, watering plants and gardens, transportation, etc.) Today we are going to learn about rivers and the water cycle. The middle part of a river is on lower ground. Some streams and smaller rivers feed into it and they are called tributaries. The river carves its own path out to the sea and creates bends called ‘meanders’. Sometimes a river becomes so bendy it creates an easier route straight across and cuts off the meander. This forms what is called an ox-bow lake.

Kaje, Janne. "Snoqualmie Watershed Water Quality Synthesis Report" (PDF). King County . Retrieved 30 January 2013. QELP - Raging River discharge". Seattle Central Community College. 26 November 1998 . Retrieved 27 December 2013. Let's start by learning about the different parts of the water cycle, as illustrated in Figure 1. (Make the attached graphic of the water cycle into an overhead transparency to show students.) The water cycle is also important to our fresh water supply used for drinking water, growing crops and industrial production. Since humans cannot drink the salty water from the oceans, we rely on freshwater from lakes, river and aquifers (underground reservoirs) to meet our needs for fresh water. When engineers alter the land by developing communities and roads, it changes the water cycle. For example, many problems with flooding in Chicago are due to the existence of so many paved areas. Originally, Chicago was built on marshy soil that absorbed significant amounts of water. Now, the heavy amount of water runoff during big storms has no place to go since pavement cannot absorb moisture. The water runs off the impermeable surfaces and into the local rivers, bringing them to dangerous near-flood levels. Engineers had the design challenge to build large underground storage tanks to hold storm water that can be used during storm-free times. Sometimes these tanks cannot hold the massive amount of water that flows as the result of a storm, so engineers in Chicago have suggested other alternatives to handle storm water runoff, including rooftop gardens, permeable alleys, green infrastructure, downspouts (which reduce the flow of water into the storm sewers), and rain gardens. Refer to the associated activity Permeable Pavement for students design and create models of rivers to see how human impacts change the permeability of riparian areas. Rivers provide critical habitat for plants and animals as well as an important source of fresh water or power for people in many cities and towns. Engineers recognize rivers as a valuable renewable resource and design ways to protect rivers and modify the flow of rivers for human benefit. They create reservoirs for drinking water, irrigation channels for growing food, and bridges for traveling across rivers. Environmental engineers study the impacts of these modifications on plant and animal habitat as well as changing floodplains and the possibilities of pollution from human activity.De-Graft: That is cool. When we talk about rivers, one word that comes up is ‘flooding’. Do either of you two know what it means? a b "Water Resources Data-Washington Water Year 2005; Snohomish River Basin" (PDF). USGS . Retrieved 5 August 2009.

What do engineers do to help rainwater flow into grassy areas, away from pavement? (Answer: They design storm drains to capture water or specific grassy areas move the rainwater from the pavement.) De-Graft: There are hundreds of rivers and streams all across England, Scotland, Northern Ireland and Wales. This is the River Severn, the longest river in the UK. De-Graft: Yeah, when a river gets too full, usually because of heavy rainfall, it can overflow or it can flood. Now, the land around a river that floods is called a floodplain.When you look at rivers like the River Severn or the Thames, you can see how there are major towns and cities along the route of the river. This is because historically people built settlements near rivers for easy access to fresh water for homes and for farming. And also because rivers have acted as easy transport routes for boats to move people and goods from place to place. But how do rivers like this begin? Permeable: This type of land cover easily soaks up excess water. Example: Land with native plants growing on it. This type of land usually has not been compacted by human activities. Within a natural or designed system, the transfer of energy drives the motion and/or cycling of matter.