HYDROGRAPHIC SURVEY
Fig. 1. The GeoSwath 250kHz transducer head on the inflatable’s customised mount.
Image: Pangea srl
The challenges of mapping small restricted sites
Carlo Peris and Tom Hiller describe an operation to perform bathymetric and topographic surveys to obtain accurate depth maps.
Carlo Peris und Tom Hiller beschreiben einen Einsatz zur bathymetrischen und topografischen Vermessung für die Erstellung von präzisen Tiefenkarten.
Carlo Peris y Tom Hiller describen una operación para realizar estudios batimétricos y topográficos con el objetivo de obtener mapas de profundidad precisos.
S
mall hydroelectric generation stations can provide local, environmentally friendly power wherever a suitable
head of water exists. By the end of 2008 ‘small-hydro’ was generating over 85gigawatts of power from installations with capacities of a few hundred KW up to a few tens of MW (compared with the Hoover dam at over 2000MW). Tese installations often use existing dams or are developed alongside new dams whose primary purpose is river water-level control or irrigation. Tere are many thousands of these small dams worldwide (over 95 000 in the USA alone) and maintaining this infrastructure requires accurate mapping and monitoring. Tis presents some novel challenges to the hydrographic surveyor and this article describes the experiences of one company providing hydrographic surveys of dams in the Apennine mountains of Italy. In 2007 Pangea Srl was contracted by
Enel SPA to perform bathymetric and topographic surveys around hydroelectric
plants located in the Lazio and Abruzzo regions of central Italy, including installations on rivers such as the Liri (province of Frosinone) and the Tiber (upstream of Rome). Te project covered many sites but each individual survey project was fairly limited in area, including some dams only a few tens of metres across. Te accuracy requirements for monitoring the sedimentation and shape of a dam floor are comparable to a ship navigation channel or dredge works. Knowledge of the water depth and total volume is required for dam maintenance and to maximise the renewable energy output. Detailed bathymetry allows improved irrigation planning and flood control, and survey images show the status of the dam infrastructure (such as the threshold and sluice gates). Accurate depth maps can also can be critical to the safe operation of the hydroelectric facility and inform the risk assessment of the dam structure. Te difficulties posed by this kind of
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