INPE's New Technology Shows Areas Prone to Flooding

Hello reader!

It follows one note published on the day (02/27) in the website of the National Institute for Space Research (INPE) that the INPE's new technology for Terrain Modeling shows areas prone to flooding.

Duda Falcão

New Technology for Terrain Modeling

Shows Areas Prone to Flooding

Monday, February 27, 2012

Called HAND - Height Above the Nearest Drainage -, the new digital terrain model developed at the Brazil’s National Institute for Space Research (Instituto Nacional de Pesquisas Espaciais - INPE) has many applications. One of the most important is to allow the advanced and widespread classification of areas that are vulnerable to floods and other natural disasters.

The HAND is created by the Group of Land Modeling from the Earth System Science Center at INPE and determines the relative gaps on the ground comparing to the rivers.

“Digital terrain model is a kind of virtual model of the landscape. The topography of the land is gathered in digital images by remote sensors – such as radar or laser, through airplanes or satellites –, then it is represented by computer as a virtual 3D surface. Mathematics computations are applied in this virtual surface to extract typical properties of the forms, such as delineation of watersheds, local rivers and streams, slopes and slope distances, among others,” explains Antonio Donato Nobre, head of the research that resulted in the new model.

The researcher at the National Institute for Amazonian Research (Instituto Nacional de Pesquisas da Amazônia - INPA), which head the terrain modeling at INPE, has been developing this new approach for 10 years. He said the model came from the quest for fundamental scientific understanding of water in the landscape, specifically the relationship between topography and hydrology. "Science works with discovery. To take advantage of scientific breakthroughs in solving problems is a responsibility of people who work with application", notes Antonio Nobre.

Archimedes' Principle

The expert explains that in a flat surface of water, as a lake, a slope for the gap is easy to determine, which allows easily knowing the spatial range of the flood. On the other hand, the flow in a non-flat land – like rivers, for example –, where there is not a clear or regular level of the water surface, is harder to refer the gap compared to the slope. Hence the difficulty in knowing where the water overflowing the river channel can reach.

Hydrodynamic models of flow can predict the range and power of floods along watercourses. However, they are complex models, usually applied in specific places, which require detailed parameterizations and are difficult to use, which restricts its application to larger scales. "The simplified innovation that HAND introduces is the intelligent way of computing the gaps. The model assumes Archimedes’ Principle, which the water chooses the shortest path to lower ground. This behavior is explained by gravity propelling water," says Antonio Nobre.

The model considers that the surface water, draining the land, traces flow paths such that each point of the landscape has a "path" connecting with the closest river or waterbody. HAND uses digital topographic information to virtually map all the flow paths of the land surface. Then the gaps along the trajectories are calculated and areas of equidistance or proximity related to waterbody are mapped, a direct measure of the likelihood of flooding.

The model has been successfully applied in regions with great incidence of flooding, such as the outskirts of São Paulo (under Megacidades project) and experimentally applied in Mundaú river, Alagoas state, and in the mountain region of Rio de Janeiro state. 

HAND model was also presented by Antonio Nobre during discussions on the Brazilian Forest Code, as a basis for a new land use. “HAND model and other advanced approaches for mapping, offer promising potential diagnostics, weaknesses and risks of each land, a key ingredient for new smart landscapes development,” concludes the expert.

The HAND development, which also involved the experts Camilo Daleles Rennó and Luz Adriana Cuartas, both from INPE, was detailed in a paper published in Hydrology and Earth System Sciences Discussions.

Source: WebSite of the National Institute for Space Research (INPE)