Floods and Droughts

1. Floods and Droughts By: Tom, Nicole, Natalie & Kelsi

2. What Causes Floods • heavy, intense rainfall • run-off from a deep snow cover • over-saturated soil, when the ground can't hold anymore water. • frozen soil • high river, stream or reservoir levels caused by unusually large amounts of rain • ice jams in rivers • urbanization, or lots of buildings and parking lots • dam malfunctions • remnants of hurricanes and even winter storms can cause flooding • El Nino causes water to flood on to land

3. When Floods Occur • In many temperate regions around the world, spring floods are common. Such floods are usually associated with snow melt or thunderstorms • Such floods are usually associated with snow melt from the winter season • Certain regions have seasons of extreme rainfall, called monsoon seasons • Floods can occur at any time of the year, depending on location • The timing of floods is largely dependent on climate and seasonal weather patterns • Coastal storm-surge floods occur in the fall and winter storm seasons • River flooding is most likely in early spring in the East, and late spring in the West • Flash floods strike during the summer months

4. Where Floods Are Most Common • Bangladesh has experienced many floods and suffered epidemics such as diarrhea because of floods • 40% of Bangladesh's land is only 1 meter above sea level, which causes it to have a large amount of floods • Extensive floods in the Mississippi River Basin during the spring and summer of 1993 caused $20 billion in damages • Floods may occur in cities, towns, farmland or normally dry valleys

5. Where Floods Rarely Occur • Floods can occur anywhere, excluding Antarctica. • Areas of highlands (high elevation above sea level) are rarely affected by floods

6. Flooding In Our Area • Harrow and Colchester South, Essex County, Ontario; widespread flooding due to 450 mm of rain in a 30-hour period (July 19 to 20, 1989) • In Toronto, Ontario, 1992, a flood caused an estimated $5 million in damage • On Lake St. Clair, Ontario, 1987, a storm with northerly winds of almost 60 kilometres per hour caused severe flood damage along Lake St. Clair, 50 evacuated, lower floors were flooded in 100 homes

7. Recent Occurrences • Nearly 6,000 New Jersey residents and 5,715 in Pennsylvania were forced from their homes by flooding that caused millions of dollars in damage on April 4, 2005 • Record-breaking floods left a trail of devastation in Cumbria during January 2005 • In March 2005, Afghanistan suffered from major flooding

8. The Potential For DestructionBecause of floods… • Businesses do not reopen and thousands of jobs are lost • On average, in the U.S. each year, nearly 75 000 people are evacuated from their homes • More than $250 000 000 in property damage occurs in the United States each year • Not only property is lost, but millions of lives each year are lost due to flooding and its effects • Thousands of people died in Bangladesh because of poor water sanitation resulting in the spread of epidemics

9. Frequency Of Occurrence • In Columbus, MS, there is an 100% chance that a flood will occur once every two years • All regions near or surrounded by water have a high percentage of being flooded sometime throughout the year (especially countries near the Atlantic) • Land use changes can have a significant effect on flood flow frequencies

10. Weather Factors Producing Floods • Storms driven ashore by hurricanes or coastal storms, torrential or persistent rain or run-off from rapidly melting snow and ice • The rate and intensity of rain fall are the two most important factors in producing floods • High levels of precipitation • When water rises above it’s boundaries

11. Exciting Facts • On the average, floods extract an annual total of 200 lives and $200 billion dollars in damage – in the U.S. alone • Flash floods are especially lethal – their sudden arrival and swiftly moving water can easily trap down unsuspecting victims • Flooding can be beneficial? Yes! Ancient Egyptians counted on the annual rise of the Nile River to water their crops and supply nutrients to the soil

12. What Causes Droughts • Droughts occur when atmospheric currents fail to carry moisture to an area • Cold currents hitting the Western coast of most continents usually causes droughts because of the dry air • A drought is usually defined as a dry period of extensive space and time (21 days with 30% of normal precipitation • Lack of rainfall is the source of all droughts • Pollution is another factor that causes droughts

13. When Droughts Occur • Droughts occur slowly, over a multiyear period • There is no universal definition of when a drought begins or ends • Droughts have occurred in several countries throughout the world • From the fall of 1975 to the summer of 1976, western Europe was plagued by a drought • In Africa frequent droughts occurring since the late 1960's have caused severe problems relating to starvation, especially in Ethiopia and Sahel, which is located south of the Sahara

14. Where Droughts are Most Common • Occasional dry spells occur almost everywhere; abnormal, persistent, and damaging dry weather constitute a drought • The Western coast of most continents are inescapably vulnerable to drought. The West has experienced a number of damaging and costly droughts, both economically and environmentally • Some climatic divisions in Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, Utah, and Wyoming experienced severe to extreme drought more than 15% of the time • Some portions of California, Idaho, Nevada, North Dakota, Oregon, Utah, Washington, and Wyoming experienced severe to extreme drought more than 30% of the time

15. Where Droughts Rarely Occur • Droughts are rare on the Eastern side of the coast due to the warm moist air moving in from the warm ocean currents

16. Droughts In Our Area • Many droughts have occurred in our area but haven’t greatly affected our ecology or economy • In 2001, our area had a period of drought which impacted crop and plant growth in River Canard

17. The Potential For Destruction • Droughts cause destruction of crops and famines • Droughts cause immense destruction to the environment and to the affected communities

18. Frequency Of Occurrence • The frequency of droughts all depends on the weather and precipitation patterns • Regions near the equator can experience two or more droughts per year • Usually hot and dry climates have droughts more frequently

19. Factors Which Produce Droughts • Minimal precipitationand extremely dry weather conditions are the cause of the most severe droughts • Extreme heat can play a major part in causing droughts

20. The extreme drought conditions which began in much of Texas in the spring of 1998 have resulted in extreme losses to Texas agriculture and those families and industries associated with it Recent Occurrences

21. The End Thank You For Your Attention