CLASS Spatial Analyst: A GIS Based Tool for Distributed Hydrological Modelling.

CLASS Spatial Analyst is a GIS tool which can be used for spatial modelling. The tool generates a number of spatial layers that can be used for many practical applications. These include climate zoning, multi-resolution DEMs, Topographic Wetness Index (TWI) / Compound Topographic Index (CTI), lateral multiple flow paths, accumulation and dispersion of water and solutes from hazard areas, estimation of soil depth, soil material/horizon distribution and soil moisture storage capacity in different parts of the landscape.

The technology used in this tool is supported by various international and national publications (eg. Tarboton, 1997; Gallant and Dowling, 2003). The tool also generates all the input files required by other models that are currently being developed and tested under the CLASS modelling framework. In particular, the multiple flow path algorithms determine the computational sequence that drives the water balance model to transfer water and solutes from upslope properties to the downslope properties and eventually to the catchment outlet. Additionally, the spatial distributions of the soils, landuse, climate and groundwater flow systems (GFS) link grid cell scale dynamics to the catchment scale effects.

CLASS Spatial Analyst is part of the CLASS (Catchment scale multiple-landuse atmosphere soil water and solute transport model) modelling framework which consists of a suite of tools required for physically based distributed ecohydrological modelling. The Department of Natural Resources (DNR) and the Cooperative Research Centre for Catchment Hydrology (CRCCH) have developed the CLASS framework. The CLASS model, its components and their algorithms are described in a detailed technical report (Tuteja et al., 2004). The tools from the CLASS framework can be used to investigate the effects of landuse and climate variability on both paddock scale and the catchment scale.

Spatial Analyst is supported by a user friendly Windows based graphical users interface (GUI). The current version is available free of cost from DNR, NSW and is operational on ArcGIS 8.3 and the Microsoft .NET platform. By September 2005, the tool will be made operational under the TIME environment developed by the CRCCH (Rahman et al., 2003) and will be available for free download from the CRCCH Catchment Modelling Toolkit website (http://www.toolkit.net.au/class). This paper outlines the basic concepts behind CLASS Spatial Analyst, describes the various functionality and presents some of the results for its application to the Little River Catchment. The details (step by step) for implementing CLASS Spatial Analyst are described in CLASS Spatial Analyst User Manual (Teng et. al., 2004).