P1A 06 Flood Risks

How often does a flood occur that is labeled as a "catastrophe"

• On average once every 200 years

• Exactly every 100 years

• On average once every 100 years

• On average every 50 years

What is the most common origin of losses in the area shown in the graph?

• Floods

• droughts

• severe droughts

• disastrous floods

How many catastrophic floods have occurred in the period shown on the graph?

• one

• two

• zero

• two hundred

The graphs shows storm graphs for an urban area and a forested area. Which line indicates a forested area?

• red

• green

How much of water added to a stream after a rainfall event in this area, may be from base flow?

• 40%

• 10%

• 25%

• 50%

How long did the flooding of the area last?

• No flooding - the sewers removed the water fast and effectively

• It flooded on Tuesday at the peak of the rainfall event

• It flooded only on Friday

• It flooded from Wednesday to Saturday

How many times is a place more likely to be flooded if it has 80% impervious surfaces and 30% has storm sewers?

• 1 times

• 2 times

• 3 times

• 5 times

One negative consequence of storm sewers is that they cause flooding. If that is the case, why do we have them in cities?

• They remove garbage from the streets

• The flooding by storm sewers happens away from the city

• They remove oil pollution from streets

• It allows water to the rats that live in the sewers

One way that deforestation is causing flooding is because it allows more surface runoff. How is deforestation also causing flooding?

• Silt is washed into the river and it can block the flow

• Logs end up in the river

• The darker surface albedo causes more rainfall in the area

• The surface is baked dry and allows more runoff

What is the main problem with channelization of a river within a city?

• It will speed up the flow of water, reducing flooding

• It will cause flooding within the city

• It looks ugly

• It will cause flooding downstream of the channelized area