## 4 Results  
### Scenario 1, Pre-Dam Removal  
Outputs of the Caesar-Lisflood LEM are analysed in a GIS environment in order to investigate the geometric changes of the fluvial system and the spatial and temporal distribution of sediment erosion and deposition and their relationships with lithology, land use, and geomorphological processes. Figure 3 shows the hillshades representing the initial DEMs used for the modeling of the two simulation scenarios. Dam removal promoted an increase of the catchment area of about 0.6 kmq. The post-dam removal catchment includes the steeper reach of the Ficocchia stream, which flows in a deep V-shape valley. As already described in the previous section, a recent work provided a comparison between LEM-based estimation of sediment flux of the Ficocchia catchment and direct measurements of reservoir sedimentation volumes [34]. This estimation covers a period (i.e., 18 years) similar to the simulation period of this work and highlights good accordance between model results and field-based data. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number** & **Land-Use Cover** & **Manning Coefficient** \\ \hline
1 & Building and road & 0.015 \\
2 & Agricultural areas & 0.035 \\
3 & Scheorophyllous vegetation & 0.05 \\
4 & Broad-leaved and mixed forests & 0.1 \\
5 & Natural grasslands & 0.03 \\
6 & Streams and water bodies & 0.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Values of the Manning coefficient. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scenario** & **Period** & **Initial DEM** & **Final DEM** & **Description** \\ \hline
1—Pre-dam removal & 0–20 yr & Pre-DR-T0 & Pre-Dr-T20 &
\begin{tabular}{c} Present-day landscape, analysis of \\ erosion and sedimentation in the \\ closed drainage system \\ Removal of dam and related \\ geographic response to base-level fall \\ \end{tabular} \\
2—Post-dam removal & 0–20 yr & Post-DR-T0 & Post-Dr-T20 &
\begin{tabular}{c} Removal of the initial DEM \\ erosion and sedimentation in the \\ closed drainage system \\ Removal of dam and related \\ geographic response to base-level fall \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Description of the simulation scenarios: the first scenario refers to the present-day geomorphological setting whereas scenario 2 infers the geomorphic changes induced by the dam removal. More specifically, LEM-based erosion volumes tend to underestimate the reservoir sedimentation of about 20%. Figure 3: Hillshades representing the initial DEMs used for the modeling of the different simulation scenarios: (**A**) pre-dam removal, initial topography (PreDR-T0); (**B**) post-dam removal, simulation period: 1 year (PostDR-T0). Simulation results of the pre-dam removal scenario are summarized in a DEM of difference (Figure 4), which shows the topographic changes at a sub-metric scale and sediment flux in the study area after 20 years. Visual inspection of the map allowed us to infer the short-term morpho-sedimentary evolution of mountain catchments and the influence of fluvial and hillslope processes on the geomorphological evolution and sediment delivery. The map highlights that erosion processes occurred along the main channels of the fluvial net whereas deposition is located in the artificial reservoir as a result of the flattening of longitudinal profiles in the lower reaches of the channels (Figure 4). Model results seem to suggest a minor impact of slope processes on the sediment yield of the studied catchment, although landslide processes and high levels of the reservoir water table have been invoked as possible factors of slight differences between LEM-based erosion volumes and direct estimation of reservoir sedimentation [34]. In any case, modelling results fit well with the spatial distribution of landforms and deposits deriving by field-based geomorphological analysis.