Fernando Alcoforado*
This article aims to present what and how to do to deal with floods in Brazil. Now, several regions of Brazil are affected by intense rains and floods that have brought deaths and destruction of buildings and infrastructure. The rulers explain the existence of this problem by the excess of rains or the overflowing of rivers, trying to exonerate themselves of the guilt of doing nothing to avoid its occurrence and its consequences. Everyone agrees that floods are natural calamities that occur when a natural bed receives a volume of water greater than it can hold, resulting in overflows. This situation can occur in lakes, rivers and streams due to heavy and continuous rainfall. Floods are considered, among the natural disasters, the ones that cause the most damage to property and the health of the population because of the direct effect of floods, secondary infectious diseases and disruptions to water and sanitation systems.
There is no doubt that today’s floods are the result of a long process of modification and destabilization of nature by human beings, which accompanies the rapid and unplanned growth of most cities. It should be noted that, in the early days of cities, the floodplains, that is, the banks of rivers, provided natural control over water. The riverine soil was prepared to be flooded in times of flood, it absorbed a good part of the water that overflowed and used its nutrients. Today, almost all floodplains in urban areas are occupied. An immense area on the banks of the rivers was also waterproofed by concrete, which increases the volume of water to be drained.
In rural areas, floods occur with less intensity, as the soil and vegetation evacuate water by suction, causing less damage. It usually occurs with less force, not reaching considerable heights that would cause the loss of property, stored food, machines and other objects. In urban areas, floods occur with greater frequency and force, causing great damage. This situation is due to human interference, thus ceasing to be a natural calamity. Human interference occurs in several stages, starting with the foundation of cities on river limits, alterations carried out in hydrographic basins, poorly designed constructions of dikes, culverts and others responsible for the evacuation of water and also by the erroneous deposit of garbage on public roads that, with the force of the waters, they are dragged causing the clogging of the water flow places (culverts and galleries).
Floods, in most cases, occur, therefore, because of human interference with nature. To prevent or reduce the effects of floods, dams and reservoirs can be built in areas of greater risk, culverts, dikes and ponds scattered throughout the city with their opening protected to prevent the entry of solid waste, in addition to promoting awareness among the population so that it does not deposit garbage on public roads and riverbeds, lakes and dams. Other actions are also important to minimize the effects of floods, including regulation and inspection by the government of land use, limiting the occupation of floodable areas to uses that do not impede the natural storage of water by the soil and that suffer small damage in the event of flooding. This zoning can be used to promote productive uses that are less subject to damage, allowing the maintenance of areas of social use, such as open areas in the center of cities, reforestation, and certain types of recreational use.
In many countries, flood-prone rivers are often carefully managed. Defenses such as dikes, reservoirs and dams are used to prevent rivers from overflowing. A dike is one of the flood protection methods. A dike reduces the risk of having flooding compared to other methods. It can help prevent damage. However, it is best to combine dikes with other flood control methods to reduce the risk of a collapsed dike. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are used. Coastal flooding has been controlled in Europe and North America with defenses such as ocean walls or barrier islands that are long, narrow strips of sand usually parallel to the shoreline.
Worldwide, the Netherlands stands out in flood prevention with an efficient defense system made up of flood control techniques developed since the Middle Ages and futuristic computer-operated steel structures that move to control floods caused by the increase in water level after storms. Dutch cities have reinvented themselves as centers of environmental ingenuity. It was the first country to adopt the construction of facilities such as parking lots that turn into emergency reservoirs. It installed squares, gardens and basketball courts in poor neighborhoods that also function as retention ponds. For the Dutch, a smart city has to have a comprehensive and holistic vision that goes far beyond the dikes and floodgates. The climate adaptation challenge includes security, sanitation, housing, roads, and emergency services.
Regardless of the actions described above, it is essential that governments at all levels (federal, state and municipal) prepare contingency plans to evacuate populations that may be affected by floods, thus minimizing the resulting deaths. It can be said that the high number of deaths in recent tragedies that hit several cities and regions in Brazil has a lot to do with the inaction of the authorities before and during the floods. The public power only acted after the tragedy, which is still a regrettable fact. Prevention is the keyword when it comes to flooding. A large part of the resources should be destined to prevention and not to cover damages as is currently the case. The municipal government has a key role in preventing floods. To this end, it must prepare a master plan for municipal development, identifying risk areas and establishing rules for the settlement of the population. According to the Federal Constitution, this plan is mandatory for municipalities with more than 20 thousand inhabitants. In addition, it must inspect risk areas, avoiding dangerous settlements, apply fines when the resident does not comply with the recommendations, prepare an evacuation plan with an alarm system and indicate areas that are safe for construction, based on zoning. Every resident must be informed of what and how to avoid being hit by the floods.
Three bodies are essential in flood prevention actions in a municipality: 1) the municipal civil defense body that is responsible for the execution, coordination and mobilization of all civil defense actions in the municipality whose main attribution is to know and identify the risks of flooding disasters in the municipality, preparing the population to face them with the elaboration of specific plans; 2) the agency responsible for the meteorology service responsible for reporting the weather forecast for the city and/or region; and 3) the community centers of civil defense, community groups that work voluntarily in civil defense activities, to collaborate with the civil defense agency aiming at the participation of the community, preparing it to give a prompt response to disasters. It is up to the mayor to determine the creation of the civil defense body, but the initiative can come from local authorities or citizens.
In addition, the city hall and federal and state government agencies should design engineering works that can prevent and mitigate the effects of floods, which are the following: 1) On highways, the implementation of steel pipes should take water by gravity away from the highways from catchment basins; 2) The serious problems of flooding in a city that has asphalted a large part of its soil would be alleviated in part by the construction of ponds, in reality large underground water tanks to store the waters underground; 3) Mandatory placement of permeable drainage floors in the huge parking lots of shopping malls, supermarkets and cinemas to allow water to infiltrate part of the soil, being the same for monuments and spaces around buildings; 4) Use of drains and gutters around all houses to divert rainwater to a reservoir or disposal area that is out of danger of flooding; 5) Maintenance, whenever possible, of some green areas so that the water is reabsorbed by the soil; and, 6) Rectification of rivers and streams, construction of dams and channels in the great rivers that overflow their containment basins.
The precautions to avoid flooding in constructed buildings are as follows: 1) keep streets and sidewalks always clean; 2) clean and unclog culverts and storm drains; 3) keep gutters and other rain flow channels free of tree branches and leaves in the houses to avoid clogging and, consequently, water return; 4) place garbage bags on the sidewalks only close to the time when the garbage collection truck will pass, preventing them from being dragged to the sewer lines when it rains heavily; 5) have a drainage pump handy in case flooding cannot be avoided; and, 6) use Dutch and British flood-proof technology as an amphibious houseboat that allows the house float in the same way as a boat.
Hydrology specialists recommend, in order to avoid flooding, the adoption of the following measures: 1) Combating erosion with the maximum reduction of silting of natural and built drainages through rigorous and extensive combat against soil erosion, as well as the irregular dumping of urban waste and civil construction debris, as well as the expansion of river gutters; 2) Combat waterproofing with the creation of domestic and business reservoirs, as well as the expansion of green areas; 3) Prohibition of traffic on high-traffic avenues when nearby rivers overflow; 4) Implementation of avenues covered by vegetation that, in cases of overflowing rivers or streams, the water would be absorbed by the soil free from paving; 5) Construction of ponds to receive rainwater and mini ponds in houses and buildings; 6) Invest in the preparation of small and large streams in the urban center to support the increase in water and act as containment barriers; 7) Review of occupied areas with continuous planning and territorial planning action; and, 8) Action and planning with the elaboration of a plan to face the occurrence of floods as well as extreme climatic variations and the construction of reservoirs capable of storing billions of cubic meters of water and its use for non-potable purposes.
From the above, it can be said that there is a solution to the problems of flooding in cities and regions of Brazil. The Brazilian population needs to hold the authorities accountable for their negligence in solving the problems of the floods and stop believing that the floods are the fault of nature or, more specifically, the rains.
* Fernando Alcoforado, 82, awarded the medal of Engineering Merit of the CONFEA / CREA System, member of the Bahia Academy of Education, engineer and doctor in Territorial Planning and Regional Development by the University of Barcelona, university professor and consultant in the areas of strategic planning, business planning, regional planning and planning of energy systems, is author of the books Globalização (Editora Nobel, São Paulo, 1997), De Collor a FHC- O Brasil e a Nova (Des)ordem Mundial (Editora Nobel, São Paulo, 1998), Um Projeto para o Brasil (Editora Nobel, São Paulo, 2000), Os condicionantes do desenvolvimento do Estado da Bahia (Tese de doutorado. Universidade de Barcelona,http://www.tesisenred.net/handle/10803/1944, 2003), Globalização e Desenvolvimento (Editora Nobel, São Paulo, 2006), Bahia- Desenvolvimento do Século XVI ao Século XX e Objetivos Estratégicos na Era Contemporânea (EGBA, Salvador, 2008), The Necessary Conditions of the Economic and Social Development- The Case of the State of Bahia (VDM Verlag Dr. Müller Aktiengesellschaft & Co. KG, Saarbrücken, Germany, 2010), Aquecimento Global e Catástrofe Planetária (Viena- Editora e Gráfica, Santa Cruz do Rio Pardo, São Paulo, 2010), Amazônia Sustentável- Para o progresso do Brasil e combate ao aquecimento global (Viena- Editora e Gráfica, Santa Cruz do Rio Pardo, São Paulo, 2011), Os Fatores Condicionantes do Desenvolvimento Econômico e Social (Editora CRV, Curitiba, 2012), Energia no Mundo e no Brasil- Energia e Mudança Climática Catastrófica no Século XXI (Editora CRV, Curitiba, 2015), As Grandes Revoluções Científicas, Econômicas e Sociais que Mudaram o Mundo (Editora CRV, Curitiba, 2016), A Invenção de um novo Brasil (Editora CRV, Curitiba, 2017), Esquerda x Direita e a sua convergência (Associação Baiana de Imprensa, Salvador, 2018), Como inventar o futuro para mudar o mundo (Editora CRV, Curitiba, 2019) and A humanidade ameaçada e as estratégias para sua sobrevivência (Editora Dialética, São Paulo, 2021) .
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