New Delhi, Oct. 1 -- The Delhi government will carry out a detailed topographic and bathymetric survey of the Yamuna stretch from Palla on the Delhi-Haryana border to Jaitpur on the Delhi-Uttar Pradesh border to map the river's underwater terrain and identify clogged sections that may be contributing to flood risk, senior government officials said on Tuesday. The study will also examine changes in the river's cross-sections and course. The topographic survey will map all physical features within 100 metres of either bank, including embankments, spurs, drains, islands, ghats and encroachments. A topographic survey charts natural and man-made features and their elevations to produce a comprehensive surface map. A bathymetric survey, meanwhile, uses sonar to measure depths and profile the riverbed, offering insights into drainage conditions and guiding future riverfront development and navigation projects. Officials said similar surveys will also be carried out for the Najafgarh drain and its main tributary, the Supplementary drain. On September 29, the irrigation and flood control (I&FC) department invited bids for the two surveys of the Yamuna. "The bathymetric survey will cover the entire 48km river course in Delhi, with cross-sections taken every 250 metres. The topographic survey will develop a contour plan of the river, track shifts in its course and record topographical changes. Both surveys will use electronic total station machines, eco sounders and sonar systems mounted on motorboats," an official said. Explaining the methodology, the official added, "Technologies such as single- and multi-beam sonar, acoustic dopplers, GPS and motion sensors will be deployed to map the riverbed. The sound velocity and sensor data will be processed using specialised software to generate a digital surface map."...