Geological, hydrogeological and hydrological conditions.
Geologically, the park area is a part of the Bohemian Cretaceous Basin, filled with sediments of the upper chalk in the Elbe facial development. It is a sedimentary chalk rock which belongs to the Martian formation ( coniacian age) . Mostly, the underlying rocks are encrusted in gray marl to limestone claystone. Cretaceous rocks form several hundred meters of monotonous formation and are relatively weak to moderately stable. The surface area is generally a sparse network of non-tectonic fissures origin and weathering processes. Residual shell marl has the character of a fluffy, sandy calcareous clay and marl, which merge into a completely weathered broken surface and a lower un-weathered surfaces with a thin plate-like separation. The output of the tertiary vein (Spojil vein) extending chalk subsoil to the east is of no interest.
Chalk sedimentary rocks are continuously covered by quaternary sediment complexes, dominating by fluvial clay to lower-grade sands. Gravel-shaped floodplains show poorly in the basal part of the cover formation, which is marked by naked river erosion, geologically preserved in the form of river shoulder fillings, today mostly fossilized under the youngest flood plains.
In our area, the old Elbe shoulder (or the original Elbe river bed), whose dominant part is a free surface, is noticeably visible on the right bank of the Elbe. The hidden part then intersects the present Elbe trough, and on the left bank it passes through in the direction of NE-SW. The “Cičák” pond in the middle is a natural relict part. The fossilized river shoulder, of a depth of 5 m, is a significant hindrance to construction work due to its soft, highly compressible organic sediments.
The abundant character of the site, formerly flooded periodically in the floodplain inundation near the confluence of the Elbe and Chrudimka, is confirmed by the continuous occurrence of fine-grained (predominantly sandy-flood) flood deposits, the so-called alluvial canal of up to 4 m. The youngest layer is anthropogenic. These are flat weirs and load-bearing bodies of line constructions that have been picked up and aligned with the original terrain.
Hydrogeologically, the chalk rock subsoil is classified into the hydrogeological region No. 4360 – Elbe chalk and the covering structure to the hydrogeological region No. 1140 – Quartet of the Elbe after Týnec.
This area can be divided into two drains:
the upper (quaternary) drain is connected to the collector of quaternary sediments with perpendicular permeability, and partly to the upper zone of the surface of the underlying chalk rocks. The drain is mainly subsidized by shore infiltration. The underground water level is slightly tense, mostly in direct hydraulic connection with adjacent watercourses. Natural flow is shallow. Water flow to NW direction. However, the locality is significantly affected by the construction of a water systems linking objects (eg, Spojil drain). This fact causes a somewhat chaotic drain of the shallow underground water.
The lower Cretaceous (basal) drain is connected to a fissure-permeable sandstone collector of the Cenomanian formation. This is a deeply imposed artesian horizon, which is irrelevant.