ORAL PRESENTATION

Before we start, we’d like to introduce ourselves. Our names are Emma and Pablo and this is our oral presentation. Our presentation is about flood.

First of all, let me tell you about “what is flooding?”.

The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water.

A flood is an overflow of an expanse of water that submerges land. It's not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.

Riverine

Slow kinds: When heavy rains, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack, the snow melts and it causes the rivers filled to overflowing their flows. This causes the land or ice fall and they cause blockages. Where causes obstruction, there happens a flood. In these cases, the water flow is slow.

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.

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.

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.

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)

Human-induced

Accidental damage by workmen to tunnels or pipes.

Muddy

A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas. Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided.

Other

Floods can occur if water accumulates across an impermeable surface (e.g. from rainfall) and cannot rapidly dissipate (i.e. gentle orientation or low evaporation).

A series of storms moving over the same area.

Dam-building beavers can flood low-lying urban and rural areas, often causing significant damage.

Effects

Primary effects

Physical damage – Can damage any type of structure, including bridges, cars, buildings, sewerage systems, roadways, and canals.

Secondary effects

Water supplies – Contamination of water. Clean drinking water becomes scarce.

Diseases – Unhygienic conditions. Spread of water-borne diseases.
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.
Trees – Non-tolerant species can die from suffocation.
Tertiary/long-term effects
Economic – Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase, etc.

Control
In many countries across the world, rivers prone to floods are often carefully managed. Defenses such as levees, bunds, reservoirs, and weirs are used to prevent rivers from bursting their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are used. Coastal flooding has been addressed in Europe and the Americas with coastal defences, such as sea walls, beach nourishment, and barrier islands.

Europe
In france government built a series of reservoirs called Les Grands Lacs de Seine (or Great Lakes) which helps remove pressure from the Seine during floods, especially the regular winter flooding.
London is protected from sea flooding by a huge mechanical barrier across the River Thames, which is raised when the sea water level reaches a certain point

Venice has a similar arrangement, although it is already unable to cope with very high tides; a new system of variable-height dikes is under construction. The defences of both London and Venice would be rendered inadequate if sea levels were to rise.
Benefits
There are many disruptive effects of flooding on human settlements and economic activities. However, floods (in particular the more frequent/smaller floods) can bring many benefits, such as recharging ground water, making soil more fertile and providing nutrients in which it is deficient. Flood waters provide much needed water resources in particular in arid and semi-arid regions where precipitation events can be very unevenly distributed throughout the year.

Freshwater floods in particular play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity.Flooding adds a lot of nutrients to lakes and rivers which leads to improved fisheries for a few years, also because of the suitability of a floodplain for spawning (little predation and a lot of nutrients).Fish like the weather fish make use of floods to reach new habitats. Together with fish also birds profit from the boost in production caused by flooding. Periodic flooding was essential to the well-being of ancient communities along the Tigris-Euphrates Rivers, the Nile River, the Indus River, the Ganges and theYellow River, among others. The viability for hydrological based renewable sources of energy is higher in flood prone regions.

Finally, the ten worst flooding in the world. How can you see, the worst floddings are in China, in the Yellow river or Youngsté river.Other, is in Indonesia when it had tsunamiin 2004. In Nerthland, North Vietnam and Colombia.

You have any question?

In my opinion, this time I don't do very well. My self-avaluation is 0,25 because I have a powerpoint and I prepared a text, but I reed it.