GRASS GIS - Simulation Models

Hydrological modelling

• See Hydrological Sciences

Rainfall-runoff modelling: TOPMODEL - r.topmodel

• TOPMODEL is a rainfall-runoff model that bases its distributed predictions on an analysis of catchment topography. The model predicts saturation excess and infiltration excess surface runoff and subsurface stormflow. Since the first article was published about the model in 1979 there have been many different versions. The idea has always been that the model should be simple enough to be modified by the user so that the predictions conform as far as possible to the user's perceptions of how a catchment works. The distributed outputs from the model help in such assessments.
• TOPMODEL page at Lancaster University
• GRASS man page r.topmodel
• GRASS man page r.topidx
• TopModel Bibliography

Watershed Calculation: r.watershed

• The series of programs provided within the watershed menu is effective for the delineation and segmenting of channel net- works, and for identifying a watershed boundary. Work is continuing to increase the effectiveness of delineating sub- basin boundaries as well.

  1.  Filtering of elevation data
  2.  Locating pits
  3.  Calculating drainage accumulation/outlining watershed
  4.  Creating stream network
  5.  Coding stream segments/finding segment lengths
  6.  Finding subwatershed basins
  

• GRASS man page r.watershed

Landscape Analysis: r.le and r.li

• Since the 1970s, with the availability of satellite data, there has been an increasing interest in the structure of the earth on the scale of kilometers or hundreds of kilometers. Landscape ecology is a multi-disciplinary pursuit, involving geographers, biologists, sociologists, remote sensors, and many others. The focus of landscape ecology is on the dynamics and structure of the biosphere, including human activities, on the scale of hundreds of meters to kilometers (Risser et al. 1984; Forman and Godron 1986; Urban et al. 1987). The science of landscape ecology expanded rapidly in the 1980s, and methods for the quantitative analysis of landscape structure also were developed (e.g. Mead et al. 1981; Gardner et al. 1987; Milne 1988; Griffiths and Wooding 1988), yet there is no generally for the quantitative analysis of landscape structure that will work within a geographical information system (GIS). The r.le programs have been designed to provide software for calculating a variety of common quantitative measures of landscape structure. The programs can be used to analyze the structure of nearly any landscape.

  The r.le programs are designed for analyzing landscapes composed of a mosaic of patches, but, more generally, these programs are capable of analyzing any two-dimensional raster or array whose entries are integer values. The r.le programs have options for controlling the shape, size, number, and distribution of sampling areas used to collect information about the landscape. Sampling area shapes can be square, or rectangular with any length/width ratio or can be circular with any radius. The size of sampling areas can be changed, so that the landscape can be analyzed at a variety of spatial scales simultaneously. Sampling areas may be distributed across the landscape in a random, systematic, or stratified-random manner, or as a moving window. The r.le programs can calculate a number of measures that produce single values as output (e.g. mean patch size in the sampling area), as well as measures that produce a distribution of values as output (e.g. frequency distribution of patch sizes in the sampling area) (Table 1), and it is also possible to output tables of data about selected attributes (e.g., size, shape, amount of perimeter) of individual patches, as well as to make new maps of patch attributes. The programs include no options for graphing or statistically analyzing the results of the analyses. External software must be used.