# A Tool for Pre-Operational Daily Mapping of Floods and Permanent Water Using Sentinel-1 Data
## 2 Data
### Validation Data  
CEMS-derived products have been mainly used to validate the open water mapping algorithm implemented in AUTOWADE. They have been generated in the framework \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Spatial Resolution** & **Revisit Frequency** \\ \hline
**Static Layers** & & \\ \hline Shuttle Radar Topography Mission (SRTM) & 30 m & - \\ CORINE Land Cover (CLC) & 100 m & - \\ Water and Wetness (WAW) & 20 m & - \\ \hline
**Dynamic Layers** & & \\ \hline Normalized Difference Vegetation Index & & \\ (\(NDVI\)) map from Sentinel 2 & 20 m & 5 days \\ Snow cover map from Sentinel 2 & 20 m & 5 days \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Spatial resolution and revisit frequency of the ancillary data. Figure 2: NDVI map updated on 12 January 2021. Gaps correspond to pixels where no cloud-free S2 data were available in the last 30 days (i.e., since 12 December 2020), or to pixels covered by snow, or water bodies. of the CEMS activations listed in Table 2. Usually, CEMS products are generated based on automatic extraction procedures, followed by an important/crucial step of validation based on visual interpretation by skilled operators. Within the CEMS portfolio, delineation products, which provide an assessment of the event's extent, have been selected. These products also include hydrography data useful to assess the AUTOWADE capability to map permanent water. For this latter purpose, hydrography data have been complemented by open water maps generated by applying the algorithm proposed in [35] to S2 images acquired under standard non-flooded conditions. The test cases in Table 2 have been selected based on the following constraints: (1) floods occurred in Europe, in order to take advantage of the Copernicus-derived ancillary data; (2) floods mapped by CEMS using S1 data; (3) floods for which a (at least partially) cloud free S2 image acquired close in time to the S1 one and under non-flooded conditions was available. In addition, events occurring in environments very different from the Italian one (like Scandinavia) have been neglected. Note that since the oldest Sentinel data are removed from the Copernicus Open Access Hub, only recent events (2019-2021) have been considered. The S1 slices used to generate the AUTOWADE-derived open floodwater/permanent water maps are listed in Table 3. It can be noted that, for each test case, even a pre-flood image has been used to generate the AUTOWADE-derived maps. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**CEMS Activation Code** & **Time Period** & **Location** & **River Basin** & **Type of Flood** & \
\begin{tabular}{c} **Area of** \\ **Interest [ha]** \\ \end{tabular} &
\begin{tabular}{c} **Estimated Flooded** \\ **Area [ha]** \\ \end{tabular} \\ \hline EMSR359 & May 2019 & Modena (Italy) & Secchia & Riverine flood & 28,000 & 283 \\ EMSR411 & November 2019 & Puget-sur-Argens (France) & Argens & Riverine flood & 39,800 & 285 \\ EMSR417 & December 2019 & Coimbra (Portugal) & Mondego & Riverine flood & 147,600 & 9460 \\ EMSR429 & February 2020 & Springfield Clonara & Shannon & Flash flood & 7900 & 546 \\ EMSR437 & May 2020 & Dax (France) & Adour & Riverine flood & 40,668 & 1850 \\ EMSR445 & June 2020 & Radauti-Prut (Romania) & Prut & Riverine flood & 95,100 & 1358 \\ EMSR492 & January 2021 & Mont De Marsan (France) & Adour & Flash flood & 103,500 & 4899 \\ EMSR496 & January 2021 & Rieti (Italy) & Turano & \& dams & 8400 & 307 \\ EMSR501 & February 2021 & Shkoder (Albania) & Buna & Riverine flood & 100,500 & 5039 \\ EMSR502 & February 2021 & Mallow (Ireland) & Blackwater & Riverine flood & 22,500 & 470 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Test cases considered in this study for open water mapping. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
\begin{tabular}{c} pre-flood \\ flood image \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: S1-GRD slices used in this study for open water mapping.