DEMHC generation from IBGE topographic maps using ArcGis software

DEMHC generation from IBGE topographic maps using ArcGis software
Gabriela Vieira Capobiango1, Demetrius David da Silva2, Hugo Alexandre Soares Guedes3, Barbara Batista Porto4

1 Majoring in Environmental Engineering, at Federal University of Viçosa (UFV); scientific initiation scholarship from FAPEMIG. (gabicapobiango@yahoo.com.br) 2 UFV third associate professor; 1A Productivity Research Fellow from CNPq. (demetrius@ufv.br) 3 UFV substitute professor; PhD researcher in Water and Environment Resources. Sponsored by CNPq.(hugo.guedes@ufv.br) 4. Majoring in Environmental Engineering, at Federal University of Viçosa (UFV); scientific initiation scholarship from CNPq. (barbara.porto@ufv.br)

Abstract: The hydrographically conditioned digital elevation models (DEMHCs) is a grid of regular valueted cells that allowed the representation of the water main way trough relief, been indicated in hydrologic studies for showing consistence between relief and superficial drainage. This paper has, as objective, presents the initial steps to generate the HCDEM from data supplied by IBGE, subsidizing it uses in hydrologic studies. In this sense, were selected three topographic vectorial maps, from the systematic mapping, scale 1:50.0000, supplied by IBGE (Instituto Brasileiro de Geografia e Estatística) on the website www.ibge.gov.br , which includes the Formoso river extension, a trybutary of Pomba river, named: Santos Dumont (26454), Paiva (26463) and Pomba river (26464). Were adopted projected coordinate system UTM (Universal Transversal de Mercator), using “Córrego Alegre” datum on 23 south zone. The HCDEM was generated using ArcGIS 10® software, having as databases vectorial level curves, spaced in 20 meters distance between one and another, higher elevation points e hydrograph already digitized. To process data on ArcMap mode, a shape file for each data was generated on ArcCatalog, corresponding to the level curves and hydrograph in polyline.dgn shape. IBGE had distributed, for free, those files already vectorized and georreferencized, and also, the hydrograph with flow direction, making easier to carrying out the work. The preparation of level curves was based on merge the disconnected lines, with “merge” command, in “Editor”, and to insert its elevation values on the attribute table. A similar procedure was done with the valuated points. The available hydrograph had presented a few imperfections, such as double river borders, discontinuity of the rivers between the maps and others nonconformities that changes the congruency relation of the generated model with reality. Therefore, it was necessary their adjustment from available tools on Spatial Adjustment interface. The prepared files (level curves, valuated points, and hydrograph of each map) were merged by “Merge” command, of ArcToolbox, and interpolated by “Topo to Raster” command, generating DEM, which it was treated, to remove undesirable characteristics, and after that, the HCDEM was generated. Finally, the model was validated comparing the generated numerical drainage with the drainage mapped by IBGE and the watershed automatic delimitation, been observed a superposition between numerical drainage and drainage mapped by 365 IBGE, considered as a Brazilian standard, and that the drainage area delimitation was consistent. The appropriate processing of data from IBGE on ArcGis software had allowed generate solids and reliable results in a fast way, compared with manual methods.

Keywords: Geographic information system, watershed, digital elevation model, topology.

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