5FloodsFlooding happens during heavy rains, when rivers overflow, when ocean waves come onshore, when snow melts too fast or when dams or levees break.Flooding may be only a few inches of water or it may cover a house to the rooftop.
6Floods Floods that happen very quickly are called flashfloods. Floods that happen very quickly are called flashfloods.Flooding is the most common of all natural hazards.It can happen in every U.S. state and territory.
7Environmental Impact of Floods Floods are important in maintaining ecosystem habitats and soil fertility.Human attempts at managing flood prone areas disrupt the natural flood cycle.
8Environmental Impact of Floods Activities such as drainage of wetlands and land clearance for farming; upstream development that replaces natural vegetation with paved asphalt; and construction of channels, levees, reservoirs change the flood cycle and often result in increases runoff, destruction of riparian habitat, and increased water pollution
9Effects of FloodsFloods destroy drainage systems causing raw sewage to spill out into bodies of water.Buildings can be destroyed which can lead to many toxic materials such as paint, pesticide and gasoline being released into the rivers, lakes, bays, and ocean, killing marine life.Floods cause significant amounts of erosion to coasts, leading to more frequent flooding if not repaired.Floods positively impact the environment by spreading sediment containing nutrients to topsoil.
10Effects of a Flood on the Ecosystem PlantsOn dry land, plant life can benefit from the sudden appearance of a large quantity of flood water.Water stored underground will be replenished by the floodwater, while soil above ground will be able to soak up the water.Plants will be able to receive water as a result.The nutrients carried by the flood water can also revive deprived plants and aid in the germination of seeds.Effects of a Flood on the Ecosystem
11Effects of a Flood on the Ecosystem Plants ContinuedFood water may prove a new lease on life for an area.The soil is likely to be more fertile, leading to a suitable area in which to grow crops.Flooding can kill woody and herbaceous plants.Effects of a Flood on the Ecosystem
12How Flooding Affects Animal Breeding The environment in are areas where floods have occurred are more suitable for the reproduction of species of birds and some other animals.Fish can breed and give birth in the areas where flood water stays for an extended duration.
13Animals Flooding forces many wild animals from their natural habitats. Domestic animals are also left without homes after floods.Rats may be a problem during and after a flood.The large amounts of pooled water lead to an increase in mosquito populations.
14Effects of Floods on Water-Based Ecosystems Coral reefs are particularly at risk from the runoff from floods.This runoff contains sediment and products such as pesticides and fertilizers, and will carry these into the ocean ecosystem.Habitats may be destroyed, and animal and plant life are is likely to suffer.Sediment may obscure the sunlight which inhibits photosynthesis of marine plants.
15Effects of Floods on Water-Based Ecosystems There are some benefits of flooding on the ocean ecosystemsThe sudden appearance of an overflow of water can wash away unneeded salt, alongside man-made products like chemical waste.This helps the flora and fauna thrive.The flood water can also sweep away junk and debris which may have accumulated by the side of rivers.
17What is a hurricaneAn intense, rotating oceanic weather system that possesses maximum sustained winds exceeding 74 mph.It forms and intensifies over tropical oceanic regions.Hurricanes are generally smaller than storms in mid-latitudes.At the ocean’s surface, the air spirals inward in a counterclockwise direction.This cyclonic circulation becomes weaker with height, eventually turning into clockwise outflow near the top of the storm.
19How Hurricanes Affect the Ecosystem Aquatic EcosystemsSediment erosion and deposition often affect oyster beds and coral reefs.Saltwater intrusion in freshwater lakes and streams causes massive fish kills and affects the lakeside habitat.
20How Hurricanes Affect the Ecosystem The hurricane floodwater often carries many toxic substances (Heavy metals, pesticides, ammonia, phosphate, untreated sewage)These substance can cause degradation of water quality, phytoplankton blooms, a decrease in dissolved oxygen and harm to many organisms.Hurricanes have minimal effect on oceanic ecosystems since the contaminants tend to be flushed out by tidal flows.
21How Hurricanes Affect the Ecosystem Terrestrial EcosystemsHurricanes wreak havoc on terrestrial ecosystems.Strong winds, storm surge, flooding and tornadoes all have an impact.Coastal wetlands and barrier islands take the brunt of the storm surge.The storm surge causes sediment to erode and shift.
22How Hurricanes Affect the Ecosystem Many barrier islands end up shifted or eroded below sea level.Mangrove forests are devastated by wind. These trees often become fuel for wildfires.This forces birds to find other places to rest.Saltwater intrusion from storm surge also changes the wetland ecosystems.Sea grass beds are often destroyed.These are critical to feeding and nesting for many animals
24TornadoesA tornado is a violent rotating column of air extending from a thunderstorm to the ground.The most violent tornadoes can have winds up to 300 mph.
25How Tornadoes FormYou need warm, moist air from the Gulf of Mexico and cool, dry air from Canada.When the two air masses meet, they create instability in the atmosphere.A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.Rising air within the updraft tilts the rotating air from the horizontal to vertical.An area of rotation, 2-6 miles wide, now extends through much of the storm.Most strong and violent tornadoes from within this area of strong rotation.
26Tornadoes Effect on Ecosystems Vegetation is uprooted.Trees can be pulled out of the ground and carried to another location.Organisms that live in or near these uprooted trees need to relocate.This can cause a loss of species of organisms could also affect the interaction between plants and animals.
27Tornadoes Effect on Ecosystems The loss of plants caused by a tornado can allow new species of plants to grow in the cleared area.Plants that survive can grow more abundantly then other species.This loss of vegetation could also lead to soil erosion.