Experimental testing of the SIBERIA landscape evolution model

SIBERIA is a physically based computer model for simulating the evolution of landscapes that links widely accepted hydrology and sediment transport models under the action of runoff, erosion and deposition over long time scales. SIBERIA is an important tool in the understanding of the interactions between geomorphology, hydrologic process and response primarily because of its ability to explore the sensitivity of a system to changes in physics, without many of the difficulties of identification and generalisation associated with the heterogeneity encountered in field studies. In this work SIBERIA is tested and calibrated against controlled landscape development. The technique adopted for testing and calibrating such a model is to compare SIBERIA to a small scale model landscape in which initial and evolutionary conditions are either known or controlled. For this purpose a landscape simulator was developed for the calibration and testing of SIBERIA. The landscape simulator consisted of a rainfall simulator which was calibrated for two different rainfall intensities. This rainfall simulator was suspended above a square box which contained erodible material in which an experimental landscape developed from precisely known initial conditions. The developing experimental landscape was recorded by stereo photographs and measured by both conventional and digital photogrammetry producing a digital terrain map of the experimental landscape surface. SIBERIA needed to be calibrated before SIBERIA could be compared to the experimental landform. Calibration was performed using a simple planar (one dimensional) catchment with one-dimensional flows. This one-dimensional catchment was constructed within the bounds of the larger (two dimensional) experimental catchment and used the same erodible material as the full size experiments and was exposed to the same rainfall conditions. This procedure ensured an independent calibration process. Once calibrated, SIBERIA was then able to be compared to the more complex planar landscape with two-dimensional flows. Two experimental landscapes were developed using different initial catchment geometry and rainfall conditions. SIBERIA simulations of the experimental landscapes using identical initial catchment geometry and rainfall conditions were conducted. Comparison of the experimental landscape and SIBERIA simulation using both qualitative and quantitative measures such as the geomorphic width function, cumulative area distribution, area-slope relationship and hypsometric curve showed a close match. The qualitative and quantitative comparisons indicated that SIBERIA is a satisfactory model of the landscapes examined.