Well,

Climate change causes variation of air and vapor pressure, variations of temperature with altitude , change in energy circulation, coriolis acceleration, wind velocity –direction, circulation of the oceans, rising sea level and absorbance of radiations. All these points’ effects appear on the distribution of cloud formation and directions, which reflect on the rainfall intensity and distribution (the main reason of floods).

Sincerely

I do not think anyone can relate flooding “exclusively” to climate change. Flooding is sometimes caused or contributed to by land use change, increases in impervious surfaces, excessive sediment (such as from landslides, gullies, etc.) causing areas of stream aggradation and lost channel capacity, channel modification causing instability or routing flow through one area just to flood another. Braided steam types have a naturally high flood frequency due to their instability and limited channel capacity. It would be extremely difficult to accurately separate out the changes caused by climate and any associated storm intensity changes from other factors as this would require an exceptionally long term climate and flow record. Some of the best records and opportunities are the long term climate and stream gauging, barometer watershed studies, and most of these efforts are less than a century old. How much can be separated from data acquired from ice and glacial storage under periods of melting threats? Geologic history shows periods when oceans were much higher and lower. Little effort has been made to estimate the occurance and effects of long term history such as paleo floods. Combining all the various tools and techniques is apt to yield some fair to perhaps good quality, educated estimates that tend to apply more to local or perhaps regional conditions than worldwide change estimates. Some areas may be subject to increased severe storms and flooding, while other areas decreased severity. Combining data, resources, share ideas and climate, hydrology, etc. and change expertise may be the best opportunity.

What about initiation of a catastrophic process by another catastrophic event. Such as a sudden seismic activity making a natural dam can cause the failure of the dams or may be a sudden change of a stream nature from effluent to influent due to the stream bed pathway creation by dissolution.

All of the above are very clear and useful.

Don't forget that floods are naturally occurring events (with or without human intervention). Any flow that exceeds the capacity of a channel is technically a flood.

What has been observed in recent decades and in recent years is the change in the incidences of extreme events and the magnitude of these events. One consequence of these changes is more frequent flooding - in certain places - or similar frequency but greater magnitude events. It is difficult to tie things down to one series of events; rather to look in a broader context to see how shifts in rainfall patterns or magnitudes impact on the ground.

In terms of linking specific events we can look at unusual recent events: the flooding in Texas last year for example. The duration and depth of rainfall was extreme, causing flooding in areas that previously had never flooded. Looking at a regional picture, it would appear that there has been a shift in the regional weather patterns, tied to hurricanes in the Gulf, which is tied to activity in the Atlantic (see previous replies). What does seem to be happening are changes that are global, regional and global in weather patterns, and that these changes are occurring more rapidly (in global terms) than had previously been recorded.

I do not think that any researcher tries to link flooding exclusively to climate change. But CC is one important factor. Frequencies and magnitudes of floods (and other hydrological events) are changing due to CC but also to other changes made to the environment (e.g. straightening of rivers, changes of land cover and infiltration and run-off patterns).