In recent weeks, Budapest and several areas of Hungary have been hit by severe flooding due to sudden rainfall.
The capital has been particularly affected, with flash floods causing serious problems in several districts.
Due to the flooding, a third level of flood protection has been declared, the lower embankment has been closed, traffic has to be reorganised in several places, the HÉV, metro line 2 and several tram lines are affected.
But why is all this happening?
A little meteorology
We already knew from the forecasts around 13 September that a Mediterranean cyclone was coming to Central and Eastern Europe that could cause problems.
These cyclones typically arrive from the Atlantic, bringing moist air masses.
They ‘stall’ at the tops of the Alps, sucking in warm air over the Mediterranean and depositing the precipitation they bring with them over the land.
These cyclones are typical from spring to autumn, but due to climate change, they now tend to arrive in autumn and move more slowly inland, so the rainfall they carry is spread over a smaller area, causing localised flash floods.
This is also the reason why the impact of cyclone Boris, which has recently arrived in Central-Eastern Europe, has become critical in the Danube and Lajta catchments.
In figures: between 7 and 14 September, the water level at the Rajka, which was around 50 cm, rose by more than 5 metres in a very short space of time, to 574 cm in 3.5 days .
( Fülke – HVG’s public affairs podcast)
There is perfect protection, but it may not be worth it
That we will see an increase in extreme weather events like the one we are experiencing now has been said by experts for decades when they talk about climate-adaptive water management.
Climate-adaptive water management is based on local, community-level vulnerability assessments that look at how exposed a community is to these events and how well it can adapt to them.
So water management at the municipal level not only looks at the risk of drought, flash floods and flooding, how many millimetres can fall and how much the water level will rise, but also considers management options: the available tools and their possible implementation, such as the sizing of ditches, sump pumps, rain gardens, underground cisterns.
The aim is not to build huge ditches, dams and reservoirs to protect against all floods, so adaptation involves accepting that streets can sometimes flood. So there can be perfect protection against flooding, but it may not be worth the investment. It is therefore the responsibility of every municipality to prepare for the most extreme weather events, including an operational warning system and protocol,in cooperation with the population.
The above shows that a complex approach to urban stormwater management is needed.
What does this mean?
Why is sudden urban rainfall a problem and how can we manage it?
Heavy rainfall is sudden and urban areas with a lot of paved surfaces cannot absorb water quickly.
This leads to flash floods, flooded roads and buildings.
But how can we manage all this?
12. district, the Municipality of Budapest, the 7.
and the 18.
The demonstration sites and other activities currently underway in the Urban Rain project, involving the 18th and 18th districts, aim to do just that: to showcase the range of tools available.
This is the approach taken:
permeable paving, gravel parking: Pestszentlőrinc-Pestszentimre (18th district), a 4+2 permeable gravel parking lot The gravel parking lot serves electric cars, because the permeability of the parking lot is to avoid possible oil spills from conventional cars.
“sponge cake”: Another project in the 18th district is a so-called “sponge alley”.
In Kolbányi Street, where water used to regularly accumulate at the bottom of the street after heavy rainfall, residents in the area used plastic chairs to signal to motorists whether or not they could drive into the street without risking getting their engines wet.
Here, underground drainage blocks, rain gardens, transverse ditches and tree trenches ensure that rainfall is stored and silted up on green surfaces, in the soil, and that it runs off more slowly to the deeper street level.
rainwater harvesting: In the districts, the project actively involved the population, distributing rainwater harvesters, several of which were equipped with measuring instruments to map the amount and distribution of rainfall.
underground cisterns: One of the demonstration projects already implemented in Erzsébetváros (7th district) the redevelopment of Klauzál Square and the installation of an underground water storage tank,which will collect rainwater from the roof of the market building and use it to irrigate the park.
climate modelling, runoff modelling, vulnerability studies: Trinity Enviro Ltd. led the development of complex models at district level.
awareness-raising workshops: The municipality of Hegyvidék (12th district) worked with HungaroMet Zrt. on climate modelling, and organised workshops for the districts and county capitals of Budapest.
distribution of rainwater harvesters: all three participating districts distributed rainwater harvesters as part of a public awareness campaign, raising awareness of the importance of rainwater conservation.
district
a comprehensive metropolitan rainfall strategy: The Metropolitan Municipality is preparing a comprehensive rainfall strategy for the capital through the Urban Rainfall project. As a first step, a detailed questionnaire on climate-adaptive stormwater management was sent to all districts, and a problem map was drawn up based on feedback from the districts. The questionnaire was followed by the acquisition of the measurement tools needed to build and refine the runoff model for the areas under study. A flat-roofed list of the capital’s institutions has also been drawn up for the installation of the meters.
With similar extreme weather situations expected in the future, urban stormwater management will become even more important, so it is important to be aware of the options.
The Urban Rain project involves 3 municipalities in Budapest and the City of Budapest.
Cover photo: Facebook
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