Univalle Researchers Are Mapping Floodplains To Minimize Risk To Life And Property

The city of Cali, Colombia is famous for its seven rivers, but researchers from the Universidad del Valle (Univalle) are researching and mapping them to reduce the risks brought by the combination of population expansion and climate change.

Professor Lina Ospina Ostios from the School of Civil and Geomatic Engineering (EICG) explained that in 2021, Cali received 77 millimeters of rain on one day in February, more than is usually received in a rainy month like January, flooding many areas of the city.

"The rivers are following and looking for the channels they always had, they don't understand that now there are people who live there," Professor Ospina said, adding that there is now a lot of urban development on the floodplains, that is, flat areas adjacent to rivers or streams, subject to recurrent flooding.

As part of the land use planning of the Ministry of Housing and Sustainable Development and in agreement with the Colombian Geological Service, Professor Ospina and an entire interdisciplinary team from the Universidad del Valle (Univalle), led by the EICG, studied the fluvial (river) geomorphology, that is, the forms of landscapes that result from the action of surface watercourses.

"If we manage the hydrographic basin in an integral way, it would be easier to prevent floods that could cause great damage or even death," Professor Ospina said.

 

Photo: Professor Lina Ospina from the School of Civil Engineering and Geomatics in the Jordan River (La Fragua). Credit: Lina Ospina.

Dykes y Disasters

In the history of the city, the rivers of Cali, including the mighty Cauca River, periodically flooded, bringing useful river nutrients for agriculture, similar to the relationship between the civilization of Ancient Egypt and the Nile River.

"For example, in the Cauca floodplain there were many wetlands and oxbow lakes whose function is to naturally absorb excess water," explained Professor Ospina.

Professor Ospina explained that in the 1950s, the process of draining the wetlands began and in 1958 the construction of the dam began, a work of hydraulic engineering built on the largest bed of the river, parallel to its banks. This allowed the swamps to be initially replaced by crops and now by extensive residential neighborhoods.

“Large dams are erected, for example along the Cauca or Jamundí rivers, with the river on one side and houses on the other… The problem is that with climate change, large amounts of rain can fall very quickly (the basins are highly degraded) and in the course of days increase the flow of the rivers, overflowing the dikes and flooding the neighborhoods built on these floodplains”, said Professor Ospina.

In his 1993 paper, Gustavo Wilches-Chaux, a counter-culture expert in disaster management, explained that “disasters aren't natural,” that is to say that the decisions of governments and other actors can increase the probability that a natural event, such as rain, will result in a human tragedy; like flooding or landslides.

"When a single person dies as a result of something that we can prevent, we already have a big problem," said Professor Ospina.

 

Population Pressure

Some of the floodplains studied by Professor Ospina cover between the south of Cali towards Jamundí, which is a corridor of urban expansion.

The professor explained that new developments, including shopping malls and residential complexes, are built on the floodplain of the Cauca and Jamundí rivers. For this reason, the new construction is on large artificial backfilled banks, but they are in high risk areas.

An unfortunate example of this occurred on June 1, 2019, where at least six newly built condominiums were flooded in Jamundí.

"It is not necessary to build houses and shopping centers on the banks of the river," Professor Opsia said, adding that it is better to build parks or nature reserves in these spaces, so that when the floods arrive there is less damage and less probability of death.

Unfortunately, Professor Ospina explained, most of the vulnerable places are low-income neighborhoods, for example, in March 2021 in Barrio Siloé, Cali, where a mother and her 4-year-old daughter died as a result of a landslide.

Read more from the School of Civil and Geomatic Engineering: Univalle is Leading Research and Innovation in Reducing Seismic Risk sísmicos 

The Aguablanca District is the former floodplain of the Cauca River. Left, in 1961 (left) and in 2007 (right) Credit: CVC (2007

International Applications And International Students

Professor Ospina said that since water risk management is a problem throughout the world, there are lessons that Colombia can learn from other countries but also teach, especially to other parts of the Global South.

"Each place is different, it has its own political and administrative conditions," explained Professor Ospina, adding that Colombia should be inspired by the current management of the phenomenon in countries like Spain, France and the Netherlands as references, but Colombia should not experience it exactly like them; you must adapt it to local conditions.

Another aspect of internationalization in this project is that in September 2022, the research group will receive a Canadian student thanks to a grant call in which their project was selected by Canada and Latin America Research Exchange Opportunities (CALAREO).

“They will come to work in the initial phase of a project where we will collect historical information that narrates events including those of hydroclimatological origin in the south of Valle del Cauca and the north of Cauca in territories of the Nasa indigenous population, within their stories, songs and legends”, Professor Ospina explained.

If you would like to contact the researchers or learn more about the projects, write to the Communications Office of the Faculty of Engineering: comunicaingenieria(at)correounivalle.edu.co

Banner photo: Geologists from the Univalle Agreement and SGC with personnel from the Risk Management office in Jamundí at the mouth of the Jordan River in the Jamundí River. Credit: Lina Ospina (2021)