Module 12: Climate and Biomes - How Can Urbanization Affect a Local Area?

What are sediment ponds and how do they work?

A sediment pond is created to catch and hold the water until some of it can evaporate while most of the runoff can seep into the ground. This prevents flooding downhill from the paved areas. Most places, such as shopping centers that have large paved parking areas, will have a sediment pond to catch runoff from the parking area as well as the rooftops of the stores.

About what percentage of all humans live in or near cities?

About 80% of people live in or near cities.

How does runoff from cities, farms and neighborhoods affect local ecosystems?

Delicate ecosystems are poisoned by toxic chemicals.

How can urban areas become cooler and have better air quality?

Mitigation (reducing) of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat.

How does a rural area cool and purify the air?

Rural areas emit (give off) infrared (heat) radiation more easily than cities because a large part of daytime energy is used to evaporate water from soil and plants. More soil and plants means more evapotranspiration can happen.

What is the main cause of the urban heat island (UHI) effect?

The main cause of the urban heat island is modification of the land surface by urban development which uses materials which effectively retain heat.

The main cause of heat buildup in cities is building parking areas and roads. Why?

The paving materials used to build parking areas and roads absorb more heat and contribute to urban heat islands.

How does population growth increase the heat in cities?

Waste heat generated by energy usage such as cars, air conditioning systems, and cooking is a secondary contributor. As population centers grow they tend to modify a greater and greater area of land and have a corresponding increase in average temperature.

What is the Urban Heat Island Effect?

a. An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas. b. The temperature difference usually is larger at night than during the day, and is most apparent when winds are weak.

Why is urban flooding due to a lack of drainage in an urban area?

a. Because there is little open soil that can be used for water storage nearly all the precipitation needs to be transported to surface water or the sewage system. b. High intensity rainfall can cause flooding when the city sewage system and draining canals do not have the necessary capacity to drain away the amounts of rain that are falling. c. Water may even enter the sewage system in one place and then get deposited somewhere else in the city on the streets.

Why do cities have less evapotranspiration than surrounding green areas?

a. Cities also tend to have less trees and vegetation within the central business district or city center. b. Less vegetation means less evapotranspiration. Like evaporation of perspiration from our skin, evapotranspiration is a cooling process.

Why is urban heat buildup a problem?

a. Heat islands can lead to increases in heat related health illnesses and deaths, b. increased energy demand, higher air conditioning costs, c. more air pollutants and greenhouse gas emissions.

How does the extra heat from a city affect the surrounding areas?

a. Monthly rainfall is greater downwind of cities, partially due to the UHI. b. Increases in heat within urban centers increases the length of growing seasons, and decreases the occurrence of weak tornadoes. c. The UHI decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams, which stresses their ecosystems.

What is Surface Water Runoff?

a. When rain or snow falls onto the earth it starts moving according to the laws of gravity. A portion of the precipitation seeps into the ground to replenish Earth's groundwater. Most of it flows downhill as runoff. b. Runoff is extremely important in that not only does it keep rivers and lakes full of water, but it also changes the landscape by the action of erosion. c. Runoff become a major problem during heavy rainfall.