Asked 31st Oct, 2021

How much rainfall/discharge can cause flooding for a given area?

I read a paper today regarding trends in drought using SPI values. That got me thinking if there is or can be an index for flooding as well. The issue is that drought is usually a long term meteorological phenomenon while flooding occurs in and for a much shorter time period than drought. So I am now thinking along the lines of the concept of rainy days where any day with a daily rainfall more than 2.5 mm is considered a rainy day. Can a similar concept be applied for flooding as well with maybe rainfall and AMC being the decisive factors? Are there any already established criteria this?

Most recent answer

13th Jan, 2022
Barlin Olivares
University of Cordoba (Spain)
Provided that the amount of rain fallen per unit of time exceeds the infiltration of that soil, flooding or excess will be generated.

All Answers (8)

31st Oct, 2021
Isaac Oluwatimilehin
Obafemi Awolowo University
Several factors can be responsible for flood. These include:
Rain intensity, rainfall duration, soil type, soil permeability, water holding capacity
drainage availability, landuse types, etc.
The same amount of rainfall in different places may not result into same condition.
2nd Nov, 2021
Kiprotich Kiptum
University of Eldoret
It depends on the soil conditions. When the soil is wet it generates a lot of runoff than when it is dry.
Look at this paper.
1 Recommendation
2nd Nov, 2021
Darren Lumbroso
HR Wallingford
As pointed out by the answers above it is challenging to have a flood index based purely on rainfall. This is because flooding is dependent on a number of other factors including the antecedent moisture conditions (AMC) and the catchment characteristics (e.g. area, slope, land use, soil type etc).
which discusses the use of the Standard Precipitation Index (SPI) to monitor flooding in Argentina which maty be of use. This paper here: looks at using the SPI to highlight wetter than normal conditions in Portugal which may lead to flooding.
1 Recommendation
5th Nov, 2021
Kiprotich Kiptum
University of Eldoret
Check on this paper of mine. It depends on the amount of rainfall and impervious surface.
1 Recommendation
10th Nov, 2021
Yurii Pavlovich Mikhailovskii
Voeikov Main Geophysical Observatory
In river valleys, floods can often occur in cloudless weather.
11th Nov, 2021
Drlatief Ahmad
University of Guelph-Ontario Canada
there are so many factors for flood like topography, land use, land cover etc and there are few indices as well for flood, even nowadays we have flood forecasting models too.
11th Nov, 2021
Ary Ahmad
Brawijaya University
if the high rainfall exceeds the infiltration capacity there are data
There is an infiltration capacity data of 8.2 cm/hour, which means that the rainfall must exceed this value. Careful research and observation is needed

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