Testing the SIMWE (SIMulate Water Erosion) model on a Martian valley system
Authors: Steinmann Vilmos , Mari László , Kereszturi Ákos 
Published: March 2020

&lt;p&gt;Surface erosion happened intensively of Mars in the Noachian, partly from precipitation and/or ice melting. However the exact method of erosion is poorly understood, despite various models are used for the Earth successfully. In this work we present the first test results of an erosion simulation GIS based system for Mars. The testing area is (2&amp;#176;55&amp;#8217; S, 111&amp;#176;53&amp;#8217; E) next to the Tinto Vallis,&amp;#160; was named after that Tinto-B. The main valley is ~ 81 km long, the average width is ~1.85 km, the average depth is ~ 250 m. From West there are several other but heavily eroded valleys, what join to the main valley. The used erosion-deposition model is SIMWE (SIMulated Water Erosion) (Mitasova et al, 2004) was applied to simulate the time limited erosion and deposition rate.&lt;/p&gt;&lt;p&gt;With the erosion-deposition simulation can also be used for targeting surface sampling missions beside reconstructing the ancient transport processes These ideal sampling locations might be barely visible on the DTMs or on the CTX, or HiRISE images - thus the modelling approach might help here also..&lt;/p&gt;&lt;p&gt;GRASS GIS 7.6 was used during the modeling starting from an elevation model and the x/y derivatives of the slope map. The script r.sim.water estimates the water depth and discharge from a simple rain event (mm/hr in min). For the erosion modelling r.sim.sediment script was used, what is the second part of the SIMWE model, what requires to calculate the detachment and transport coefficient and the shear stress of the analysed area.&lt;/p&gt;&lt;p&gt;The shear stress was determined az 1.0 as a default value, like the transport coefficient (value=0.01). The detachment&amp;#160; coefficient was calculated from the estimated K-factor of the analysed area and the calculated specific weight of water. The model use a 15mm/hr rain in 5 minutes long.&lt;/p&gt;&lt;p&gt;The results from the test area clearly show the main falls and debris skirts and also show the smaller erosion areas, what are not abundant on CTX and can&amp;#8217;t be determined on the HRSC DTM. Using Earth based values as a first and rough approach, the transport limited erosion-deposition ranges from 0.0180 kg/ms&lt;sup&gt;2&lt;/sup&gt; to -0.0166 kg/ms&lt;sup&gt;2&lt;/sup&gt; where the positive values show the erosion and the negative values the deposition. Based on the experiences, we aim to develop further the model and adjust the physical parameters for more Mars relevant conditions. In the future we plan to running simulation, what show the possible landscape evolution in the past and in the future&lt;/p&gt;&lt;p&gt;Reference: Mitasova, H., Thaxton, C., Hofierka, J., Mclaughlin, R., Moore, A., &amp; Mitas, L. (2004). Path sampling method for modeling overland water flow, sediment transport, and short term terrain evolution in Open Source GIS. Computational Methods in Water Resources: Volume 2, Proceedings of the XVth International Conference on Computational Methods in Water Resources Developments in Water Science, 1479-1490.&lt;/p&gt;