INFLUENCE OF THE METHOD FOR CREATING A DIGITAL ELEVATION MODEL ON THE RESULTS OF SOIL LOSES CALCULATION

Abstract

Problem Statement and Purpose. The problems of digital elevation model (DEM) creation are very actual and being investigated comprehensively. DEM is widely used for solving different problems which are connected with the modelling of nature processes. Relief is the important object of investigations. DEM has got a special role in modelling and assessment of soil water erosion, hi interpretation and estimation of modelling results the question of accordance of DEM and processes which are researched is appeared. This question is solved by field researching, comparative geographic method and GIS-technologies.The purpose of the research is the assessment of the influence of the DEM which are created by different interpolation methods with the same topographic data on the calculations of potential soil loses. Soil loses are estimated by the GIS-realized mathematical model of rainstorm erosion losses of soil which are developed in physical geography and nature management department of Odessa National I I. Mechnikov university.Data & Methods. The research territory is situated in Prychernomorska lowland (Kherson region Bilozerskyi district). It is a little valley with 40-50 m height amplitude. The hills have got different profile forms and steepness. The climate is temperate continental. Soil cover is presented by calcic chernozems.Height dataset is created by Maplnfo Professional 6.0 instruments. For this purpose, the topographic map 1:25000 was digitized. The digitizing square is about 70 sq.km. Ordinal kriging. triangulation with linear interpolation and radial basis functions like interpolation methods were used for DEM creation. The interpolation procedure was performed in Golden Software Surfer environment. Because of the implementation of mathematical model of rainstorm erosion losses was made in PCRaster the DEMs were converted in this GIS-package and the assessment of soil loses was performed. Morphometric analysis was made by using standard functions of SAGA GIS-package. Slope steepness and length, root-mean-square error (RMSE) and the compliance with the DEM and topographic basis were assessed for analysis.Results. It is determined that all chosen interpolation methods have controversial influence on calculation of potential erosion loses by using GIS-realized mathematical model of rainstorm erosion losses. The main statistics characteristics which are calculated differ from each other in different limits especially it concerns the extreme values. The influence of interpolation methods is manifested in mathematical differences of morphometric relief values on different DEM. The maximum differences between topographic data and interpolated model are observed on DEM which is created by triangulation with linear interpolation. That differences are noted in results of soil loses calculations too.Positive deflections of interpolated heights are characteristic of thalwegs, bottoms and collecting slopes of fluvial and erosion forms, and negative ones - watershed surfaces and scattering slopes.Difference between DEM in slope steepness was not noted, but in length it amounts to 35 % for DEM which created by triangulation with linear interpolation. RMSE is too different for all DEMs.It is recommended to use DEM which take into account the deviations of relief morphometric values no more than 5 %. It is better to use such DEM in modeling of soil erosion loses and planning of any agricultural or business activity. So the best interpolation methods are kriging and radial basis functions.The reflection accuracy of relief plastic plays the main role in case of choose of DEM as the base of modeling. Especially it concerns such characteristics as transverse and longitudinal slopes profiles and their various genetic combinations in space.