TerraHydro proposes a different computational representation for dealing with water flow in GIS applications. These applications involve the concept of local flow, extracted from terrain, which is the basis for most spatially explicit distributed hydrological models.
Different computer structures based on regular grids, triangular irregular networks, contour lines, and irregular polygon tessellations have been used to extract local flow, entirely linked to the data structure chosen for terrain representation. Then, each local flow set requires its own specific extraction algorithms, as well as different formats to store its associated local flow.
TerraHydro proposes a data structure based on Graph Theory that unifies computer local flow representation, independent of the data structures used for terrain representation permitting that a set of operations for water management be formally defined over this new structure.
Each triangle side starting or ending as a local flow represents a graph node. Local flow goes from one side to another side of a triangle, passing through their middle points. The graph nodes identifiers are the same associates to the triangles sides during the triangulation process.
When a local flow goes along a triangle side, the vertices of that side represent graph nodes. The graph node identifier corresponding to triangle vertex is computed adding the total number of triangles sides to the vertex identifier from triangulation.
The local flow goes from each cell to one or more neighbors, passing through their centers. The graph node stores the cell identification number and a graph edge is a link between two cells. Multi flow issue is intrinsic in the contour lines data model. Each cell represents a water flow uniform space.
Each Voronoi polygon is a graph node and each graph edge represents a link between two neighbor polygons. Graph nodes store the Voronoi identification numbers existing in the Voronoi data structure which is similar to the grid cell approach.
TerraLib - Open-source GIS software library. TerraLib supports coding of geographical applications using spatial databases, and stores data in different DBMS including MySQL and PostgreSQL
TerraView - GIS application built using the TerraLib GIS library. TerraView main goal is to make available to the GIS Community an easy geographic data viewer with resources that include database queries and data analysis, exemplifying the use of the TerraLib library
TerraHydro is a TerraView plugin, using all TerraView funcionalities Database TerraLib TerraView Plugins Plugins Hidro
LDD Extraction: for each grid cell the local flow is defined considering the steepest downstream regarding the 8 grid cell neighbors. LDD is the basis for developing applications involving water resources.
Upscaling definition: redefinition of local flows in a grid of lower resolution from the local flow extracted from a high resolution grid (LDD)
River reaches: define drainage segments, between water springs and junctions, between junctions, or between junctions and mouth of the drainage.
Basin delimitations: the delimitations can be done by selecting one or more points over the drainage. TerraHydro finds the basin for each given point or for each river reach basin .
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TerraHydro – Example Accumulation Area / Drainage
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