Survey and bathymetric campaign of Lake Idro and surrounding areas - Brescia, Italy

“Topko was very useful to integrate a topographic campaign already performed earlier. The union of the new survey with the existing ones was instant and fast, just as the generation of a single DTM”.

Marcello Cesaratto
Surveyor
GlobaRT Servizi Topografici

INFORMATION

Company:
GlobaRT Servizi Topografici
Via Montello 50/a
Zoppola (PN)
ITALY

Tel: +39 0434 974089
Fax: +39 0434 974089
E-mail: info@globart.org
Web: www.globart.org

SOFTWARE

SierraSoft softwares used

LINK

Survey and bathymetric campaign of Lake Idro and surrounding areas

Integration of the topographical surveys related to the final design for the safeness of Lake Idro.

Company description

GlobaRT was founded in 2003 from the union of experiences in different topographical areas and the desire of a young group to create a 360° topographical company. These objectives are the strength of a team that now operates nationally providing their professional skills and know-how in the survey field to provide support to road, civil and industrial design. GlobaRT, faithful to the young and dynamic spirit that has always distinguished it, has made technological innovation the instrument to ensure a high quality service, designed on the needs of the customer. The possession of GPS equipment of the latest generation (which are able to work with permanent stations), robotic total stations, digital levels of precision and highly specialized software, demonstrates the company’s desire to create products with added value, both in terms of representation and in its contents.

The project

The project involves the implementation of the hydraulic safeness of Lake Idro. Its main inlet is the Chiese River which is also the natural outlet of Lake Idro and, after being extensively used for irrigation in the south part of Brescia, it flows into the Oglio River. Lake Idro is the first Italian natural Lake that has been subjected to artificial adjustment with a dual purpose: irrigation and hydroelectric production. The first reason that generates the need of making Lake Idro safe is the presence of an active landslide that is affecting the left bank of the Chiese River. The topographic measurements performed since 1985 have shown that the entire landslide mass, made particularly plastic in periods of heavy rainstorms, is slowly sliding downhill. The observation of the movement in action clearly indicates that the landslide mass has not yet reached a final equilibrium configuration and this leads to consider the situation very dangerous and the possibility t hat, in cases of particularly intense and prolonged bad weather conditions, the movement of the mass could accelerate leading up to more or less landslide, invading the valley below. In addition to the presence of a landslide already briefly mentioned, the work on the safeness of the lake is also necessary to replace the current drain structures as the actual adjustment works have functional, geometrical and of state of preservation characteristics, that can not guarantee the security of the coastal and valley areas even in the absence of a landslide collapse. For the preparation of the final design of the project for the hydraulic safeness of Lake Idro, new surveys were made to supplement what was achieved in the preliminary draft. For approximately 3 km downstream of the Abbioccolo torrent, 21 additional sections were then surveyed which were necessary for the hydraulic modeling. Lastly, for the completion of the cartography of the external areas outside the surveyed zones, we made use of the laser scan survey made by Chiese Consortium. The maps obtained were then superimposed on the CTR cartographies of the Idro and Lavenone municipalities. The operations of the campaign of measurements were done as follows: connection of the IGM elevations with hydrometer; planimetric and altimetric connection of all surveys performed; implementation of a digital terrain model with Prost connecting the pre-existing surveys to the new ones made, through new triangulation calculation; insertion of the surveys on the technical regional papers; additional surveys of the hydraulic works (tunnel access); bathymetric survey of a belt of 100mx50m (perpendicular to the shore) with a mesh 10mx10m circa; integration of the ground survey of the area between the road and the lake shore for about 140m upstream and 100m downstream of the existing survey; a few points have also been integrated on the upper side of the road to better describe the works of the tunnel entrance close to the maneuver room; creation of an XYZ near the existing side road with the plani-altimetric insertion of the handiwork; creation of an XYZ of the shores with the survey of two additional sections of the river bed; extension of the XYZ near the way-out of the tunnel, with extension of the right hand shore of the Chiese River also including the smaller stream affluent on the right and the soccer field; the survey of 25 sections downstream from Lavenone to Vestone, one every 200 m, with a full description of the riverbed and banks up to an altitude above the maximum flood level, after the completion of the soil tests the heads of the holes of sampling were surveyed and plani-altimetrically placed.

Technical difficulties

The main difficulty encountered during the survey is related to environmental factors; the surveys were conducted in aquatic environments along river courses with lush vegetation; in addition, being a mountainous area, the accessibility to the survey sites and travel within the same were particularly problematic. From a technical viewpoint, however, the first obstacle was to import the surveys carried out in a previous topographical survey, provided in DWG format; Prost being compatible with this format made the operation virtually automatic, thus providing the possibility to convert drawing entities into topographical entities. Another problematic aspect that was successfully resolved with ProSt was the merging of the data coming from multiple survey techniques. The surveys campaign required the use of different types of detection: bathymetry, total station survey, GPS (statics and RTK with both autonomous base and VRS). For the latter, in particular, and in addition to the main points provided by the contracting authority, even the IGM grill for the transformation of coordinates in the Gauss Boaga system had to be used. The final part of the work, that was the creation of a single DTM model resulting from the union of the previous topographical surveys with those carried out by us, was fully completed in a simple and fast way by using the full potential of Topko.

Details of the project


  • Bathymetric: 100 x 50 m perpendicular to the shore 10 x 10 mesh
  • Survey on the ground: about 4000 points beaten.
  • Hydraulic sections found on the Chiese river: 25, one every 200 m - development sections 1602.33 m.
  • Datum points: 7

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Some pictures of the work

General planimetry of the intervention

General planimetry of the intervention

Display of the survey on Google Earth

Display of the survey
on Google Earth

Celerimetric survey

Celerimetric survey

Hydrometer

Hydrometer

Chiese River

Chiese River

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