Today, there are several ways to prevent flooding. In this regard, two methods of dam construction and reforestation (or afforestation) are in competition. But which one is scientifically more effective? Which one is used in your country? Is there any more successful way to prevent flooding?
Dear Dr. Jahani,
Thank you for sharing your question. As you are well aware Iran is currently under heavy rain and we are witnessing lots of damages due to flood in different parts of country. So discussing this important subject is essential.
10 measures that must be taken to prevent more flooding in the future
Source: https://www.independent.co.uk/news/uk/10-measures-that-must-be-taken-to-prevent-more-flooding-in-the-future-a6788866.html
As per my opinion both dam and reforestation will play important role in flood control. The area which are more prone to floods should be reforested with deep rooted plant species.
Dear Ali
There is relatively limited evidence that afforestation has a significant effect on reducing extreme floods (i.e. floods with a discharge with an annual probability rarer than 1 in 20 years) on large catchments (i.e. ones that drain areas greater than 50 km2). This paper called “Is planting trees the solution to reducing flood risks? (see: https://www.researchgate.net/publication/326445643_Is_Planting_Trees_the_Solution_to_Reducing_Flood_Risks) states that following “a systematic review and meta‐analysis of direct evidence for the effect of tree cover on channel discharge. The results highlighted a deficiency in direct evidence. From seven eligible studies of 156 papers reviewed, the results show that increasing tree cover has a small statistically significant effect on reducing channel discharge”.
As mentioned above the best way of reducing flood risk is via a portfolio of structural (e.g. flood defences, storage) and non-structural (e.g. flood warnings, spatial planning) measures.
I hope that this is of help.
Best regards
Darren
If you are looking for perfect answer, I would say both. However in my personal opinion reforestation and building a good drainage system is more important. Nobody knows about future. Last week unexpected rains dropped in my home city which has never happend in the past 100 years and all 5 huge dams became full. City had to discharge dam’s water in order to prevent dam failure. As a result, flood occured and a large part of city got demolished due to flood, lack of plants and a good drainage system, mismanagement...
https://www.google.com/amp/s/www.cbc.ca/amp/1.5087723
Mahmoud Omid : Dear professor Omid, I really appreciate for sharing your opinions.I do agree with you. Today I see that dam constructors are using this situation make a force on society for starting new dam projects. They define the flood protection as the main reason for the construction of new dams. Therefore we should avoid creating new dams with side-effects.
Darren Lumbroso : Thank you Darren. I am reading your suggested paper. Maybe new strategy should be consider for rare floods to reduce the side effects because these kinds of floods are natural phenomena.
Mohammadreza Habibi : That is really happening in Iran which is so disappointing.
In the boreal forest zone, wetlands are widely seen as key flooding mitigators. See e.g. Article How Wetlands Affect Floods
and
https://www.sciencedirect.com/science/article/abs/pii/S0006320710001461
Many muskeg/wetlands/mires have historically been ditched/drained in Fennoscandia, and the trend there is to recreate/restore these wetlands. The reason can be, among other good reasons, to reduce the risk of flooding.
Back Tomas Ersson : thank you Tomas. what do you think about artificial wetlands? do you know any experience about them?
The Nordic countries have extensive experience of aritficial (aka constructed) wetlands.
For example, the Swedish Meteorological and Hydrological Institute ( https://www.smhi.se/en) has a GIS-database over artificial wetlands in Sweden: http://vattenwebb.smhi.se/wetlands/
Without being an expert on the matter, I have not noticed any difference in opinion on natural vs artificial wetlands when it comes to ecosystem services like flood control, nutrient retention, sediment trapping, etc.
It depends on the region characteritics
Take a look at this link:
https://www.charteredforesters.org/2017/06/trees-can-reduce-floods/
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