# Groundwater and Urban Planning Perspective
## 3 Discussion of Urban Planning and Subsidence
### Analysis of the Subsidence Triggering Factors in Clotentina River Corridor
As an example, for the Intrarea Chefalului area, situated on the left shore of Tei Lake, near the area indicating subsidence, on the northeast, there is an area where changes were detected. The values of negative subsidence are higher on the border of the two types of areas. From the other available information, it was evident that in the area with land changes detected, construction work took place and was finalized in mid-2019. This work can contribute to the ground displacement values in the neighboring area. Figure 8: Areas showing land-cover changes and vertical displacements for the periods 2004–2010 and 2014–2018. Map generated in Esri\({}^{\oplus}\) ArcMap\({}^{\text{TM}}\) 10.3. Base map source: OpenStreetMap. Source: elaborated by the authors. The map presented by Figure 9 brings together both areas with potential instability and areas showing land-cover changes, and areas with negative vertical displacements determined from PSI maps generated from Sentinel-1 data for 2014-2018 and ENVISAT ASAR data for 2004-2010. Most of the subsidence areas, both for the 2004-2010 and 2014-2018 periods, are in regions that have been determined to have the potential for instability, generated by construction activity and outlined by the land-cover changes or historical activities in terms of quarries for building materials or similar. In the vicinity of the lakes of Coletina, an important land-cover change yet to be mentioned is the drainage of some areas which in the past were part of the lakes of Coletina and are now urban areas. These are highlighted in shades of red in Figure 9. In some areas (e.g., the embankment zone of Soseau Nordului), partial stabilization of the area could occurred between the analyzed time intervals due to the interruption of the construction works or by completion of the buildings settlement processes. Four of the 37 instability areas are further discussed, namely Promenada, Pod BV, Gara Herastrau, and Soseaua Nordului. Table 4 provides the processed information used in the analysis: the name of the area; Sentinel-1 orbit used to generate the PSI map; the behavior of the area during the period 2004-2010; the average annual velocity along the line of sight (LOS); the distance between the centroid of the area and the lakes; the presence of anthropogenic soil and its thickness; the thickness of the loess layer; the previous area situation (water or swamp cover identified in the historical maps); the presence of a career of construction materials used in the past; the geology of the area; the monitoring of borehole locations nearby each area; the depth of the shallow aquifer strata (Coletntina gravels); the depth of the water table of the shallow aquifer (unconfined). Changes of  
Figure 9: Areas showing subsidence and instability potential. Map generated in Esri® ArcMap  
the shallow aquifer groundwater hydraulic head matches the chained lake's water level variation as their bed shows a direct hydraulic connection to the shallow aquifer. Located on the left bank of Lake Floreasca, at a distance of over 500 m, the areas Promenada, Pod BV, and Gara Herastrau (Figure 8) are characterized by the presence of anthropogenic deposits or as being used as the location for previous construction materials quarries. The construction work that carried on during the period preceding the 2014-2018 interval in these areas as well as in neighboring ones represent the identified land-cover changes. Most of these land-cover changes are related to the construction of high office buildings. Table 4 shows the comparison between the evolution of the water level in the Floreasca Lake and the evolution of the values of the vertical terrain displacement. Even for both, there is a general downward trend during the period when the water level of the Floreasca Lake decreased at a sharp pace; a steeper downward trend for vertical terrain displacements has been registered (Figure 10).