## 2 Materials and Methods
### Computation of Indicators  
First, to determine the exact scope of the analysis, the current configuration at the official level of the structure of natural channels in the area was taken into account. Unregulated channels with a level greater than 3 according to the Horton-Strahler criteria [39] were selected, in order to generate a representative model of the current hydrom morphometric situation of the theoretical natural hydrographic network in the Campo de Cartagena area (Figure 7).  
To contrast the distribution of the real floodplain produced by the latest DANA in comparison to the situation expected by the current theoretical models of the regulations, an _NDVI_ analysis was carried out to identify the changes in land cover during the DANA days. The Normalized Difference Vegetation Index (_NDVI_) is a land cover analysis index used to estimate the quantity, quality, and development of vegetation based on the measurement of the radiation intensity of certain bands of the electromagnetic spectrum that vegetation emits or reflects. For the calculation of this vegetation index, the information found in the red and infrared bands of this electromagnetic spectrum was used. The calculation of the _NDVI_ was done using the following formula:  
\[NDVI=\frac{NIR-Red}{NIR+Red} \tag{4}\]  
where _Red_ and _NIR_ stand for the spectral reflectance measurements acquired in the red (visible) and near-infrared regions, respectively. This method allows us to identify all the areas in which the rains have produced a flood plate on the surface of the basin regardless of whether or not damage has occurred in an area. In this way, the areas subject to runoff because of the rains were identified. The data were obtained through the Sentinel 2A and 2B satellites with an accuracy level of 10 m for the days in which the DANAs of the years 2016, 2018, and 2019 occurred.  
Then, the GIS analysis was undertaken using a constructed 5 m\({}^{2}\) digital elevation model (DEM) of the Campo de Cartagena area to assess the statistical correlation between the anthropogenic process of the territory from the case study and the increase in its vulnerability to flooding. Laser imaging detection and ranging (LiDAR) tools from the IMDA LiDAR SDI [32] are used to implement relevant elements such as urban areas, wadi orography, and the slopes of the agricultural crops in the DEM (Figure 8).  
Figure 7: Area of study selected following a watershed model based on Horton–Strahler criteria established by national regulations.  
Once the distributions at the spatial level of the flooding impact and territorial anthropization indices were generated, we evaluated the possible spatial correlation between them using geostatistical tools. For this, the territory needs to be \"discretized\" as a continuous element in \(100\times 100\) meter cells in order to numerically evaluate the spatial correlation between indicators with specific values on a continuous space. These cells were assigned values according to the results obtained in the _NDVI_ analysis and the GIS cartography database for the damage of the DANAs. On the other hand, anthropic values were obtained for the indicators of territorial transformation of historical GIS cartography for the years 1956, 1981, and 2016. The cartography detailed data are summarized in Table 2.