Determination of watershed geosystems structure by means of GIS-based modeling (by example of small riverswatersheds of Tomsk outskirts)

GIS-based modeling has had a significant role in scientific research in physical geography lately. GIS-based modelingallows conducting mathematical modeling of the geosystem component structure ( vegetation distribution in the relief, soil texture,moisture, etc.), functioning (runoff, insolation dose distribution, etc.); solving the tasks of creating the landscape ecology monitoring;improving the hydrology processes prediction, especially in the conditions of information deficit. The paper investigates the part of theUshaika River watershed (8 km from the outlet) and the Samuski River watershed (15 km from the outlet). The northern and westernriver watershed boundaries are determined by the ''catchment area'' morphometric indicator on the basis of structure-hydrologicalanalysis of DEM. The southern and eastern boundaries of river watersheds were outlined on current topographic maps (1: 25000) andtopoplans (1: 10 000). The approach of geosystem mapping on the basis of GIS-based modeling consists in the combination oftraditional methods and techniques and introduction of technological elements based on pure mathematical algorithms. The procedureincluded two consequent blocks - geoinformational analysis and field observation and measurements. ''Multi-Resolution Valley BottomFlatness'' (MRVBF) [1] is used for automatized allocation and correction of field measurements of the areas, which potentiallycoincided with rivers floodplains. ''Wetness index'' [2] is used to determine the moistening mechanisms of the areas. Erosion potential ofgeosystems is estimated by ''LS-factor'' [3]. The comparative analysis of key topographic attributes distribution proves the importance of''Wetness index'' for geosystem differentiation. The indexes of area moistening of the Samuski watershed is considerably higher that thatof the Ushaika. This feature influences the active distribution of the processes of area swamping and water-logging. The inclusion of therange of topographic attributes in geosystem mapping allows objectifying the processes of geosystem boundaries determination. Thus,the comparison of MRVBF model with the data of the floodplains field mapping showed high geosystem boundaries correspondence.The indicators of the erosion potential of the geosystems correlate with the surface slopes angles in most cases.

Keywords

Authors

References