drought
defined
impacts
causes
atmospheric blocking
measures of drought: Drought Index A drought index assimilates thousands of data on rainfall, snowpack, streamflow and other water-supply indicators into a comprehensible picture. A drought index is typically a single number, far more useful than raw data for decision making. • Percent of normal precipitation (PNP) • Standardized Precipitation Index (SPI) • Palmer Drought Severity Index (PDSI) • Surface Water Supply Index (SWSI) • Reclamation Drought Index • Deciles (monthly drought)
Palmer Classifications 4.0 or more extremely wet 3.0 to 3.99 very wet 2.0 to 2.99 moderately wet 1.0 to 1.99 slightly wet 0.5 to 0.99 incipient wet spell 0.49 to -0.49 near normal -0.5 to -0.99 incipient dry spell -1.0 to -1.99 mild drought -2.0 to -2.99 moderate drought -3.0 to -3.99 severe drought -4.0 or less extreme drought PDSI
PDSI
Palmer Drought Severity Index
Types of Floods 1. Riverine Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoons, hurricanes and tropical depressions, and warm rain affecting snow pack. Unexpected drainage obstructions such as landslides, ice, or debris can cause slow flooding upstream of the obstruction. Fast kinds: include flash floods resulting from convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.
Great Flood of 1993
Types of Floods 2. Estuarine Commonly caused by a combination of sea tidal surges caused by storm-force winds. A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. 3. Coastal Caused by severe sea storms, or as a result of another hazard (e.g. tsunami or hurricane). A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. 4. Catastrophic Caused by a significant and unexpected event e.g. dam breakage, or as a result of another hazard (e.g. earthquake or volcanic eruption)
Katrina flooding
Dec 26 2004 Tsunami Picture of Banda Aceh before and after 2004 Tsunami
Primary effects of floods 1.Physical damage - Can range anywhere from bridges, cars, buildings, sewer systems, roadways, canals and any other type of structure. 2.Casualties - People and livestock die due to drowning. It can also lead to epidemics and waterborne diseases.
Secondary effects of floods 1. Water supplies - Contamination of water. Clean drinking water becomes scarce. 2. Diseases - Unhygienic conditions. Spread of water- borne diseases. 3. Crops and food supplies - Shortage of food crops can be caused due to loss of entire harvest. However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil. 4. Trees - Non-tolerant species can die from suffocation.
Tertiary/long-term effects effects of floods 1. Economic - Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase etc.
blizzard
many people had to move And then the dispossessed were drawn west — from Kansas, Oklahoma, Texas, New Mexico; from Nevada and Arkansas families, tribes, dusted out, tractored out. Carloads, caravans, homeless and hungry; twenty thousand and fifty thousand and a hundred thousand and two hundred thousand. They streamed over the mountains, hungry and restless--restless as ants, scurrying to find work to do — to lift, to push, to pull, to pick, to cut p anything, any burden to bear, for food. The kids are hungry. We got no place to live. Like ants scurrying for work, for food, and most of all for land. — John Steinbeck, The Grapes of Wrath, 1939
Jamestown, Virginia
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