# Groundwater and Urban Planning Perspective
## 3 Discussion of Urban Planning and Subsidence
### Analysis of the Subsidence Triggering Factors in Clotentina River Corridor  
The study area has been defined by using a buffer zone of \(1\) km on both banks of the Coletntina River. It starts from the northwest area of Bucharest, from the entrance to Herastrau Lake, and ends at the exit of Pantelimon II Lake, in the southeastern part of the municipality (Figure 3). Based on the vertical displacement PSI maps of the land surface for the 2004-2010 and 2014-2018 intervals, it was possible to analyze the evolution of vertical displacements in the Coletntina study area. Figure 6 shows the evolution of the terrain instability in the studied area. The areas that presented subsidence during the period from 2004-2010 are highlighted in red. Areas with negative vertical displacements during the period from 2014-2018 are outlined in purple [28]. In most of the cases, in the immediate vicinity, the areas overlap during the two time intervals. This is the case for the areas situated on the right shore of the Tei, Colentina, and Pantelimon I Lakes, as well as some of those situated on the left shore of Floresca and Colentina Lakes. For the subsidence areas situated on the right shore of Tei Lake, a detailed study is presented in [38], the main factors involved in the ground displacement process being the presence of a thick anthropic soil, the dynamics of the water supply losses in the area from 2006 to 2014, and the decrease in the area groundwater hydraulic head. For the 2014-2018 period, there are several areas showing subsidence without having a correspondent to the previous period from 2004-2010. These new subsidence areas occurred due to construction work extensions in areas where other categories of use were previously involved (e.g., the pasture area replaced by residential area in the area situated on the left shore of Pantelimon II Lake; the industrial area replaced by a commercial center in the area situated on the right shore of Fundeni Lake, near the border of the study area). The current extension of the lakes has been delineated using Open Street Map data [63]. From the land-cover change detection map generated from Sentinel-l GRD data for the Colentina River buffer zone, the areas where land use changes occurred during 2014-2018 have been identified. Figure 7 shows the map for determining the land-cover changes, along with these areas. The identified areas are marked in blue. Figure 6: Subsidence areas in the Coletina River buffer zone, for the time intervals 2004–2010 and 2014–2018 [28]. Map generated in Esri® ArcMapTM 10.3. Base map source: OpenStreetMap. Source: elaborated by the authors. Figure 7: Land-cover changes for the Coletina River buffer zone modified after [28]. Map generated in Esri® ArcMapTM 10.3. Base map source: ESRI. Source: elaborated by the authors. These areas include:  
* Areas covered with vegetation in 2014 on which high buildings (residential complexes) were built until 2018;
* Areas covered with vegetation in 2014, which were transformed into residential districts with houses until 2018;
* Areas where infrastructure elements have been developed (e.g., parking extensions, construction of new parking lots for already built buildings);
* Areas with buildings that have been demolished and where new buildings have been built;
* Areas covered with construction sites where the works were completed by 2018 [28]. Figure 8 shows the areas with land-cover changes during 2014-2018 (marked in brown) as well as the areas showing vertical displacement during the two studied time intervals, 2004-2010 (red color) and 2014-2018 (purple). Some areas with land-cover changes are independent of areas with subsidence or uplift. However, it is evident that there are also areas where the two types of phenomena occur in the immediate vicinity. In many cases, this happens due to the extension of construction work into distinct residential areas. The combined analysis of the two types of phenomena can help when looking for the factors generating subsidence and their localization.