# ERS-1/2 and Sentinel-1 SAR Data Mining for Flood Hazard and Risk Assessment in Lima, Peru
## 3 Results
### No Flooding
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Category Code** & **Description** & **Numbers of Changes** & **Area (Man2)** \\
**No Flooding (NP)** & & & \\ \hline Motorway construction & Construction of the highway called “Naova Autopista & & \\ (NF1) & Centrale (NAC)” (New Central Highway) & & \\   Vegetation cover-corpland changes (NF2) & Increase or decrease in vegetation cover (nowing/novering). & & \\  & Also included cultivated areas that have suffered a variation in & 27 (18) & 5.50 \\  & & land use & \\  & & & \\ \hline \multirow{2}{*}{Exphemeral changes (NF3)} & \multicolumn{2}{c}{Parked vehicles (e.g., trucks, goods loading/unloading} & \multirow{2}{*}{15} & \multirow{2}{*}{0.60} \\  & & activities). They are located near the sales companies or & & \\ (NF3) & & factories of different types of products & & \\ \hline
**NR1** & \multicolumn{2}{c}{Mercury meshes are} & \multirow{2}{*}{2} & \multirow{2}{*}{0.20} \\
**NP5** & \multicolumn{2}{c}{Vehicle traffic} & & \\  & & & \\  & & Raising water content in the treatment tanks. These changes & & \\  & & have been identified in the water/water treatment plans & & \\ \hline \multirow{2}{*}{Landini-earthworks (NF7)} & \multicolumn{2}{c}{Sull deposit, to prepare the area for a change in land use} & \multirow{2}{*}{7 (2)} & \multirow{2}{*}{0.20} \\  & & & \\ \hline
**NR5** & \multicolumn{2}{c}{Sull movement/identified as country zones} & \multirow{2}{*}{22} & \multirow{2}{*}{1.80} \\ \cline{2-2} New building constructions & \multicolumn{2}{c}{New construction areas (heds/new urban areas)} & \multirow{2}{*}{26 (5)} & \multirow{2}{*}{8.40} \\ \cline{2-2} (NP9) & \multicolumn{2}{c}{Waterhouse areas} & \multirow{2}{*}{10} & \multirow{2}{*}{2.30} \\ \cline{2-2}
**NF11** & \multicolumn{2}{c}{Cemetery areas} & \multirow{2}{*}{1} & \multirow{2}{*}{0.01} \\ \cline{2-2}
**Road construction** & \multicolumn{2}{c}{Rods under construction (Moradze & \multicolumn{2}{c}{7 (1)} & \multirow{2}{*}{0.18} \\ (NF12) & \multicolumn{2}{c}{Marez/Lurigiancho/Gamnetta)} & & \\ \cline{2-2} Archaeological excavations (NF13) & \multicolumn{2}{c}{Archaeological remains} & \multirow{2}{*}{4} & \multirow{2}{*}{0.20} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Description of the changes categories in the radar backscatter related to anthropogenic events. Numbers reported in parenthesis indicate how many changes of the total for the given category were considered for the subsequent flood risk assessment due to their local slope or proximity to the Rimac River. Grey background mark the categories of changes that were not relevant for flood risk zoning. Figure 13: Distribution of changes in the radar backscatter, likely due to human activities (anthropogenic), observed and mapped within the Rimac River basin. due to the movement of machinery, workers, landscaping, among others, thus resulting in a non-homogeneous signal backscatter (Figure 14). These changes are located on alluvial deposits, with slopes in A and B-class (23 and 14 changes, respectively), and in non-urbanized areas. * Vegetation cover-cropland changes: there are 18 changes, located in non-urban areas and on alluvial deposits, and with A-class slope (\(\beta\leq 5^{\circ}\)), due to growing crops or land use changes, e.g., transition to new residential/commercial buildings (Figure 15). * Ephemeral changes: increase in the radar backscatter was observed in 15 areas as a consequence of an increase in the number of vehicles parked (Figure 16). These changes are located on a slope between A and B-class, on alluvial deposits, with eight changes on non-urbanized areas, and the other seven on urban areas. * New building constructions: these five changes are considered important for risk assessment, since they have a low slope (A-class), and in conjunction with their proximity to the river, they match with elements that can be easily flooded. They are located on alluvial deposits, and in urban areas (Figure 16).