# Investigation of Rain-On-Snow Floods under Climate Change
## 3 Results and Discussion
### Climate Change Scenarios
#### 3.2.2 Frequency and Magnitude  
In the next step of this study, we also investigated how the frequency (i.e., number) and magnitude of ROS floods could change in the future. The methodology described in Section 2.4 was used to define ROS floods. The median values calculated based on the results of five GCM/RCM models of ROS floods for the period 1981-2010 were 13 and 15 events for the Soca and Gradascica River case studies, respectively. Table 2 shows the relative difference in the number of ROS floods (i.e., median value of all five models) for the periods 2011-2040, 2041-2070, and 2071-2100 compared to the baseline period. One can notice that generally we could expect an increase in the number of ROS floods in the future. This increase is the highest for the period 2041-2070 for both considered catchments. The only exception is the period 2011-2040 when a slight decrease was observed compared to the baseline period for the Gradascica River case study (Table 2). Similar results were also obtained by [5; 9], who found that the frequency of natural hazards and ROS floods could increase in the future. Additionally, similarly as for the seasonality investigation there are large differences among the five investigated cases.  
Figure 3: Examples of the seasonality investigation for different global/regional climate models (GCM/RCM) models showing all ROS floods (circles) and resultants (i.e., average values) indicated with arrows of different colors for different periods. (**a**) Soca River for Case 1, (**b**) Soca River for Case 2, (**c**) Gradascica River for Case 3, (**d**) Gradascica River for Case 4.  
Changes in ROS-flood magnitudes were investigated in the next step. Figure 4 shows box-plots of ROS-flood magnitudes (Q) for different 30-year periods for both selected case studies. According to Figure 4, it can be understood that a range between the maximum and minimum discharge values seems to be higher for the future periods (2011-2040, 2041-2070, and 2071-2100) compared to the baseline period (1981-2010) for the Soca river for all GCM/RCM models. If we compare median values for the Soca catchment, one model (i.e., Case 1) predicts an increase in ROS floods magnitudes. On the other hand, three models (i.e., Cases 2, 4, and 5) predict smaller values in the future. The median values of all ROS floods for all five cases shown in Table 2 indicate a decrease in the ROS-flood magnitudes in the Soca River catchment in the future compared to the baseline period. On the other hand, it is true that the most extreme ROS-flood magnitudes could increase in the future (Figure 4). Similar results were also obtained by [38]. Similarly, as for the Soca River catchment all models predict that the magnitudes of the most extreme ROS floods could increase. For the Gradascica River, which has temperate continental climate characteristics, the magnitude of ROS floods seems to be higher in the 2011-2040 compared to the baseline period for the Cases 1, 2, and 3. Results shown in Table 2 indicate that median values of ROS-flood magnitudes for the Gradascica catchment could slightly increase in the future. However, in other future periods, ROS-flood magnitudes have a changing pattern in comparison to the baseline period for each climate model.  
Figure 4: Box-plots of ROS-flood magnitudes for four investigated 30-year periods for two catchments and five GCM/RCM models. Box-plot colors indicate different periods (yellow: 1981–2010; blue: 2011–2040; orange: 2041–2070; green: 2071–2100).