Fernando Alcoforado*
At the present time, several regions of Brazil are affected by intense rains and floods that have brought deaths and destruction of buildings and infrastructure. Government officials explain the existence of this problem by excessive rainfall or by overflowing rivers trying to avoid the guilt of doing nothing with the adoption of preventive measures. On 07/30/2018, we published on the Academia.edu website the article The engineering deficit in the solution of the floods problem in Brazil. In this article, we affirm “this is an unjustifiable explanation because there are resources of Engineering for a long time that would allow to prevent great rains or overflow of waters in rivers and streams from flooding roads and cities. The problem exists, therefore, not due to the lack of engineering techniques capable of solving it. The problem is one of incompetence or disinterest by governments (federal, state or municipal) in solving the problem. The flooding of roads and cities by rainwater or by the overflow in rivers or streams is inconceivable in the current era”.
Flood control concerns all engineering methods used to reduce or prevent the harmful effects of rainwater and river floods. Some methods of flood control have been practiced since Antiquity. These methods include planting vegetation to retain excess water, sloping terraces to decrease the slope flow and building alluviums (man-made channels to divert floodwater), building dikes, dams, reservoirs or holding tanks to store extra water during flood periods. Some of the common techniques used for flood control are also the installation of rock shoulders that hold loose blocks and assist in drainage, rock ripraps composed of compacted rock blocks, sandbags, maintenance of normal slopes with vegetation or application of soil cement on steeper slopes, concrete curtains and construction or expansion of drainage channels. Other methods include dikes, dams or detention basins.
The engineering works that can prevent and mitigate the effects of floods are as follows: 1) On highways, the implantation of steel pipes should take water by gravity away from the road from catchment basins; 2) The serious flooding problems in a city that has paved a large part of its soil would be partly alleviated by the construction of swimming pools, in fact large underground water tanks to store the water underground; 3) Mandatory placement of permeable draining floors in the huge parking lots of shopping malls, supermarkets and cinemas to allow water to infiltrate part of the ground, the same for monuments and spaces around buildings; 4) Use of drains and channels around all houses to divert rainwater to a reservoir or disposal area out of danger of flooding; 5) Maintenance, whenever possible, of some green areas so that the water is reabsorbed by the soil; 6) Rectification of rivers and streams, construction of dams and channels in the large rivers that overflow their containment basins; and, 7) Implementation of a civil defense system that should be able to at least warn people and have a scheme to remove them from homes in time with some belongings and house them.
The precautions to avoid flooding in constructed buildings are as follows: 1) keep streets and sidewalks always clean; 2) cleaning and unblocking manholes and wolf mouths; 3) keep gutters and other rain flow channels in the houses free of branches and leaves of trees to avoid clogging and, consequently, water return; 4) placing garbage bags on the sidewalks only around the time the garbage collection truck will pass, preventing them from being dragged to the sewer networks when it rains heavily; 5) have a drain pump at hand if flooding cannot be avoided; and, 6) use Dutch and British flood-proof technology as a floating amphibious house that allows the building to float in the same way as a boat.
In summary, hydrology experts recommend, to avoid flooding, the adoption of the following measures: 1) Combating erosion with reduction to the maximum extent the silting up of natural and constructed drainages through rigorous and extensive combating soil erosion, as well as irregular dumping of urban waste and civil construction debris, as well as the expansion of river channels; 2) Combating 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 lanes of avenues covered by vegetation that, in cases of overflow of rivers or streams, the water would be absorbed by the pavement-free soil; 5) Construction of swimming pools to receive rainwater and mini swimming pools 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 spatial 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 their use for non-potable purposes.
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 methods of protection against flooding. A dike reduces the risk of flooding compared to other methods. It can help prevent damage. However, it is best to combine levees with other flood control methods to reduce the risk of a collapsed levee. When these defenses fail, emergency measures, such as sandbags or portable inflatable tubes, are used. Coastal floods have been controlled in Europe and North America with defenses such as ocean walls or barrier islands that are narrow, long strips of sand usually parallel to the coastline. In the world, the Netherlands excels in flood prevention with an efficient defense system composed of flood control techniques developed since the Middle Ages and futuristic steel structures operated by computers, which move to control the floods caused by the increase in the 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 become emergency reservoirs. It installed squares, gardens and basketball courts in poor neighborhoods that also function as retention ponds. For the Dutch, a smart city must have a comprehensive and holistic vision that goes far beyond dikes and floodgates. The challenge of adapting to the climate includes security, sanitation, housing, roads, and emergency services. From the above, it can be said that there is engineering solutions to the flooding problems on highways and large Brazilian cities. Technical solutions exist to avoid the damage caused by flooding on the highways and on the population of large cities, especially the poor populations who systematically lose their assets when they face floods. The Brazilian population needs to hold the authorities responsible for the negligence in solving the flood problems and to stop believing that the floods are the fault of nature.
* Fernando Alcoforado, 80, 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, em co-autoria) and Como inventar o futuro para mudar o mundo (Editora CRV, Curitiba, 2019).
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