*2.2. Long-Term Simulation in the EROSION-3D Model*

Although the EROSION-3D model has mainly been established as an event-based model, it contains the possibility of executing long-term simulations as an additional tool [29]. The long-term simulation submodel has a continuous character and can perform long-term simulations and run more calculations one after the other; after each event, the digital elevation model is adjusted to reflect the amount of erosion and deposition [25]. Long-term simulations can be performed in the following ways [30]:


#### **3. The Case Study**

The Svacenický Creek catchment, which has a total area of 6.3 km2, is located in the Western Slovak Republic in the middle of the Myjava Hill Lands (Figure 2). The climate is continental, warm and moderately humid, with a mild winter and warm summer. The mean annual precipitation in the catchment is between 650 and 700 mm (1981–2015); the mean annual temperature is about 8.8 ◦C (1981–2013), as measured at the Myjava meteorological station. The elevation ranges from 311.4 m to 545.6 m a. s. l. The Svacenický Creek catchment is part of the flysch massif of the White Carpathians, and the dominant type of soil is Luvisols (68.0%), followed by Pararendzina (28.7%), and Cambisols (3.7%). The relief is composed of moderate slopes in the lower part of the catchment and narrow stream valleys with steep slopes in the upper part. The aerial-photograph from 2018 was used for creating of land use map and the arable land covers almost 66% of the catchment (Table 1).

The Svacenický reservoir (Figures 2 and 3) was constructed in 2010 at the bottom of the Svacenický Creek catchment as a flood-protection measure, and the permanent water level covers approximately 3 ha of the catchment. According to the project documentation [31], the height of the embankment dam is 10.25 m and the maximum retention capacity is 215,808 m3 with a maximum water level of 8.5 m. The planned minimum water level height is 4.4 m (316.4 m about mean sea level (AMSL)). The modelled retention capacity during a 100-year flood is 207,330 m3, with a peak discharge of 16.0 m3·s<sup>−</sup>1.


**Table 1.** The land use categories in the study area.

**Figure 2.** The characteristics of the Svacenický Creek catchment study area: (**a**) Relief, soil samples and location in the Slovak Republic; (**b**) land use; (**c**) textural soil unit (TSU) and World Reference Base (WRB(FAO)).

**Figure 3.** The Svacenický reservoir: (**a**) The autonomous underwater vehicle (AUV) EcoMapper path and longitudinal/transversal profiles; DEM of the reservoir in (**b**) 2015, (**c**) 2016, and (**d**) 2017; Graphs of the bottom's development—(**e**) longitudinal profile, (**f**) transversal profile A, (**g**) transversal profile B.
