engleski

Morphometry of Red Lake using LiDAR and SoNAR technology

Red Lake in the Dinaric karst (Croatia) is the exceptional karst phenomena, world wide known for its beauty and extreme depth. Even so, through the history of Red Lake’s research there were many controversies in the conclusions and the theories concerning its genesis, geomorphology and hydrology. This work has for a goal to give an overview of existing findings about Red Lake as well as to present the newest research results won with the help of emerging technologies based on LiDAR (Light Detection And Ranging) method and hydro acoustics. For the first time the precise morphometry for the Red Lake is given which is known to be one of the deepest karst lakes in the world. The measurements took place during September 2013. New generation of equipment developed to advance the geoscientific research has been deployed during the field work and the gathered data enabled the analysis which led to a new understanding of the lake’s morphology. The LiDAR survey resulted with obtained set of data "cloud point“, where each point has a defined position in space. The cloud point was filtered with respect to outliers and noise. Data collected using LiDAR methods provide accurate digital elevation model, which can be used in further analysis and modelling. For the purpose of underwater investigations of the lake the remotely operated underwater vehicle, commonly referred to as an ROV was deployed, equipped with a HD camera, precision compass with gyro and SoNAR (Sound, NAvigation and Ranging) for hydro acoustics survey. ROV can accurately measure the depth of the dive and the geometry of the horizontal sections in spherical coordinates. Images are recorded at different depths with the sonar device placed on the ROV. Operating frequency of the sonar is 670 kHz and the power of transmitted signal is 23 dB. Such configuration of the device can provide registration of echo at distances up to 600 m in ideal conditions. The results gave a new insight into geometry of the deepest karst lake in the world as well as into functioning of the karstic lake. The further research on Red Lake involves the regular LiDAR scanning of the lake’s shores above the water surface in order to determine the amount of fallen material between the two recordings as well as the rate of collapsing process. The research will also consist from periodical temperature and dissolved oxygen records and continuous monitoring of water turbidity. It is from crucial importance to expand the scope of future measurements and to simultaneously measure the hydrological parameters in Blue and Red Lakes with the option to monitor other karstic water phenomena in the vicinity. An insight into the regional direction of circulation of groundwater would be possible with adequate spatial distribution of deep piezometers in the study area. The availability of new technologies in hydrological and geomorphological measurements opens up new possibilities in the study and monitoring of the karst aquifer as well as karst phenomena such as Red Lake. Every new research work and scientific results based on measurements using modern technology enrich and complete the overall knowledge in karst hydrology. This should be a guideline in the future scientific research of the functioning of Red and Blue Lakes near Imotski.

karst; LiDAR; hydro acoustics; modeling

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