Extreme precipitation events that occurred between March 24 and March 26 of 2015 in the region of the Atacama Desert (26-29 degrees S) left around 30000 victims, being one of the biggest events over the past 50 years, with total a cost of reconstruction of about 1.5 billion dollars. The mudflows which increased during the flashflood inundated much of the city of Copiapo and Tierra Amarilla. This manuscript aims to model the mudflow of March 2015 in the Rio Copiapo, specifically in the towns of Copiapo and Tierra Amarilla. The modeling process is performed using the Rapid Mass Movement Simulation Model (RAMMS) that allows modeling the dynamics of the mudflow in two dimensions, only using the topographic features of the modeling domain. Calibration of the model was carried out successfully using data from inundation heights captured around the city after the 2015 event. A detailed analysis of the hydrometeorological event is carried out using satellite images obtained from Multi-satellite Precipitation Analysis (TMPA), and pluviometric and hydrographic data available in the Copiapo River basin. The simulation of the flood is reproduced with maps of inundation heights associated with two modeling scenarios. The maximum flood heights are ultimately used for developing risk maps at both sites. According to our results, the RAMMS model is an appropriate tool for modeling mudflow and mapping flood risk to improve hydrological risk management in arid and semiarid basins of Chile.