Flood Descriptions:
Coastal Flood - Hurricanes and tropical storms can produce heavy rains, or drive ocean water onto land. Beaches and coastal houses can be swept away by the water. Coastal flooding can also be produced by sea waves called tsunamis, giant tidal waves that are created by volcanoes or earthquakes in the ocean.
River Flood - Flooding along rivers is a natural event. Some floods occur seasonally when winter snows melt and combine with spring rains. Water fills river basins too quickly, and the river will overflow its banks. Often the land around a river will be covered by water for miles around.
Urban Flood - As undeveloped land is paved for parking lots, it loses its ability to absorb rainfall. Rain water can not be absorbed into the ground and becomes runoff, filling parking lots, making roads into rivers, and flooding basements and businesses.
Flash flood: A flash flood is a sudden flood event caused by a hydrologic response of the drainage basin. Flash floods are normally strongly localized and associated with extreme showers or thunderstorm activity, when high rates of precipitation occur in a short period of time.
Flash floods usually arise when rain falls over a small catchment basin. The terrain may channel the extreme run-off to produce a flood peak that reaches its maximum in just a few minutes or hours. Flash floods are increasingly observed in urban areas where the surface is unable to absorb large amounts of water in a short period. Often the impetus and velocity of flood water are much more important than the associated water levels and duration in terms of potential impact on population and structures.
flood endangered areas flood prone areas
Methodology:-
The aim of the research presented in this paper was to gain insight in the perceptions of the local stakeholders in the Laver and Skell catchments on the link between land management and the risk of flood generation and to explore solutions in the Laver and Skell catchments with them. For this purpose, interviews were held with farmers, and a stakeholder workshop was rganised, during which the FARM(The Floods and Agriculture Risk Matrix) tool was sed to facilitate the discussion. The paper is organised as follows: section 2 presents the conceptual framework on land management and flood risk. The FARM tool is described in section 3, and the research methodology in section 4. Section 5 gives the results of the farmer interviews and the stakeholder workshop. The stakeholder perceptions are compared with current scientific evidence in section 6. The last section presents the conclusions.
The main objective of our study is to investigate the effects of historical land-use change on the flood risk of reclaimed lands. The study area is a reclaimed land of 76km 2 located in the plain of the Po River near the city of Bologna (northern Italy). We implemented a semi-distributed rainfall-runoff model to different historical land-use scenarios from 1955 to 1992 and considered rainstorms associated with different exceedance probabilities, so as to quantify the impacts of the observed land-use dynamics on the flooding potential of the study area.
For a more definite assessment of the effects of landuse changes on the hydrologic behaviour of the study catchment an investigation of the uncertainty of our model is a fundamental requisite. This issue will be addressed in future and more focussed analyses in a gauged catchment. The different approaches to uncertainty assessment in hydrological modelling can be broadly divided into two main categories: (1) statistically- based techniques (see e.g., Krzysztofowicz, 2002; Montanari and Brath, 2004), and (2) simulation and re-sampling methods (see e.g., Kuczera and Parent, 1998; Beven, 2001; Beven and Towards, 2002), and neither one can effectively quantify model uncertainty without an extensive amount of observed streamflows.
History Of Flood Is Important
flooding is not a modern phenomena and reconstruction of historical flood events is an essential step in the modern flood risk management The identification and quantification of historical flood events could help planners and engineers in determining the return periods (Payrastre et al., 2005) and a better assessment of extreme flood events. Also could help to know the trend of the frequency and magnitude of floods over the past few centuries.
Flood Risk
Flood risk is defined by the probability of flooding and the potential damage caused by the flooding. Flooding is expected to increase in the future because of the impact of the climate changes and as a consequence of human actions on the landscape (Brown and Damery, 2002; Reynard et al., 2001). Flooding endangers the people life and property and because of increasing population living in floodplains, the damaging effects of the flooding is potentially rising.
Therefore, flood risk and flood risk management have gained a great concern. We could not avoid the damaging impacts of flooding however, an integrated strategies across farmers, farm owners, government, local authorities, internal drainage boards, water companies and emergence services may help to mitigate the potential economic and health costs and raise the risk awareness of the general population while enhancing sustainable development (Defra, 2004b).
The strategies of flood risk management should be diversed and regionalized according to the type of flood and the area in which flood happen (Hooijer et al., 2004b).
Flood risk management may involve structural process (eg. river engineering and flood defence) and non-structural process (such as flood warning, land use regulation).
Along with climate, land-use change can theoretically modify the volume and timing of local storm runoff (see Table III). Despite significant changes in land use and management practices in the UK over the last 50 years, there is very little evidence that any effects on flood peaks at catchment scales can be isolated from climate variability (Defra, 2005b). Even where detailed hydrological records and documented land-use changes co-exist, no obvious trends emerge (Hiscock et al., 2001).
Flooding is defined as is a temporary situation resulting from failing of the normal confines of surface water (river, lake, streams, sea) or from accumulation of water as a result of heavy rainfall in areas with poor drainage. In these situations water level and/or discharge exceed a critical level, causing water to escape from their normal confines. However, this does not always cause flooding (Munich-Re, 1977).
Flood generation depends on the means in which rainfall is transformed into river discharge. This could be affected by a number of factors including: characteristics of the precipitation, pre-flood soil moisture conditions, the transfer mechanism of rain to stream flow, the size and shape of the stream flow and timing of events (Hooijer et al., 2004a).
Flooding has become more frequent and severe because of global climate change and human induced changes in the natural environment (Brown and Damery, 2002; Reynard et al., 2001).
Climate Changes And Flooding:
Over the late 20th century, there was an increase in global mean surface air temperature by about 0.6°C + 0.2°C and this affected the global hydrological cycle (Glen, 2004). In the UK, the temperature has been risen since the mid 1980s (Sparks, 2009). By the end of 2100, it is predicted that the global surface temperature is likely to increase by about 1.5-3.5oC. This increase in surface temperature will enhance evaporation and as a result, rainfall and runoff will be accelerated.
Jenkins et al 2007, reported that since 1766, the annual mean rainfall has not changed considerably in England and Wales, however, there was a slight increase and decrease in precipitation during winter and summer respectively (Jenkins et al., 2007). As a result, there will be more water in winter and less water during summer in the landscape (Dawson et al., 2001; Estrela, 2001) and this will not be without bad effects. Throughout the UK, the heavy rainfall events were up trending over the past the forty five years (Abrahams, 2008).
Rising Sea Level
Global warming contributes to the increased rate of rising sea level because of thermal expansion of seawater; snow melting (the effect of ice melting depends on location and amount of accumulated ice, and the timing and rate of temperature rise) and increased precipitation.
Sea level has risen and fallen throughout history and prehistory and this is likely to be more serious in the coming decades. Now, the rate of rise on the east coast of the UK is around 5-7 millimetre/ year and it is predicted that the sea level in the Hull will increase by one metre in the coming 100 year than the level nowadays (Winn, 2009).
Since the last ice age, sea level has risen and in concomitant with this the whole country has been tiling due to the loss of the weight of the ice. Therefore, water versus land levels has changed in this part or the country by around two millimetres per annum (Winn, 2009).
What is happen in Sheffield and Hull in 2007, and York in 1998 and 2000 are examples of the extreme weather events.
