Results of a modified physical based erosion model (SIMWE) on a Martian environment
Authors: Steinmann Vilmos , Kereszturi Ákos 
Published: October 2020

The erosion on Mars is poorly understood, especially the fluvial erosion, which modified obviously the surface of the Red Planet. There are several erosion models for the terrestrial environment. These models are without climbing completeness: USLE, USPED and SIMWE [1]. All of the listed models use physical variables, but most physical variables are available on SIMWE (SImulated Water Erosion) model. These are: elevation model, first order derivative of the slope (E-W and N-S direction), runoff infiltration rate, Manning&#8217;s value, rain event duration (min) and unique value (mm/hr), detachment coefficient, transport coefficient, critical shear stress. These variables are divided in two different GRASS GIS scripts: r.sim.water [2] and r.sim.sediment [3].&#160;&#160;A former simulation used the SIMWE model on a Martian valley system, which is near to Tinto Vallis, in this case it is called Tinto B (2&#176;55&#8217; S, 111&#176;53&#8217; E). The first type of SIMWE model used the erodibility parameter (K-factor, based on the TES dataset), 15 mm/hr rain event, which held 5 minutes and used the default given parameter for the detachment (Dc) and the transport (Tc) coefficiente and critical shear stress. With these settings the SIMWE model gives a detailed map, which shows the small drainages, which are non- or barely visible on the CTX images. The second version of the model modified parameters, which come from the THEMIS thermal-inertia dataset. The K-factor sand related variable was modified with the normalised value of the thermal-inertia (local maximum of thermal-interia = 1). The variables for the detachment and transport coefficients were calculated also from the thermal-inertia values, and are equivalent with the sediment diameter sizes [4]. These converted sizes re related to the Shields parameter and critical bed shear stress [5]. From these variables the the detachment and the transport coefficient can be determined with the following equations: Tc=A/(&#120566;*&#120588;w1/2*gM) [6]; Dc=Kfac*(&#120591;-&#120591;c) [7], where Tc - transport coefficient, Dc - detachment coefficient, &#120566; - Shields parameter, &#120588;w - density of water, gM - Martian gravity, Kfac - erodibility factor, &#120591; - shear stress, &#120591;c - critical shear stress, A - variable from (cikk). The produced new estimated erosion-deposition map gives more detailed results, than the results in phase 1 [8], especially on the accumulation region of the small drainages. These more detailed results can give more information about the possible points of interest for further missions.&#160;The model is still under improvement to adapt to the Martian environment. In this second phase the detachment and the transport coefficient have been determined, using the dataset of THEMIS thermal-inertia. In this case, all of the applied elevation datasets for the SIMWE model have to be reducatet to 100 m/px.&#160;Acknowledgement: This work was supported by the GINOP-2.3.2-15-2016-00003 fund of NKFIH&#160;References:[2] Neteler, M. and Mitasova, H., 2008, Open Source GIS: A GRASS GIS Approach. Third Edition. The International Series in Engineering and Computer Science: Volume 773. Springer New York Inc, p. 406.[3] Mitasova, H., Thaxton, C., Hofierka, J., McLaughlin, R., Moore, A., Mitas L., 2004, Path sampling method for modeling overland water flow, sediment transport and short term terrain evolution in Open Source GIS. In: C.T. Miller, M.W. Farthing, V.G. Gray, G.F. Pinder eds., Proceedings of the XVth International Conference on Computational Methods in Water Resources (CMWR XV), June 13-17 2004, Chapel Hill, NC, USA, Elsevier, pp. 1479-1490.[4] Fenton, Lori. (2003). Aeolian processes on Mars: atmospheric modeling and GIS analysis. (Phd thesis, CALIFORNIA INSTITUTE OF TECHNOLOGY )[5] Berenbrock, Charles; Tranmer, W., Andrew; Simulation of Flow, Sediment Transport, and Sediment Mobility of the Lower Coeur d&#8217;Alene River, Idaho, 2008, USGS Scientific Investigation Report, pp 43.[6] Lamb, M. P., Dietrich, W. E., and Venditti, J. G. ( 2008), Is the critical Shields stress for incipient sediment motion dependent on channel&#8208;bed slope? J. Geophys. Res., 113, F02008, doi:10.1029/2007JF000831.[7] M.S. Kuznetsov, V.M. Gendugov, M.S. Khalilov, A.A. Ivanuta,; An equation of soil detachment by flow; 1998;&#160; Soil and Tillage Research,; vol 46; issues 1-2; pp 97-102[8]Vilmos, Steinmann; L&#225;szl&#243;, Mari; &#193;kos, Kereszturi; 2020; Testing the SIMWE (SIMulate Water Erosion) model on a Martian valley system; EGU 2020 abstract; Wien