Delhi govt to conduct topographic, underwater terrain surveys of 48-km Yamuna stretch

Delhi will conduct topographic and underwater bathymetric surveys of the 48-km Yamuna stretch from Palla to Jaitpur to map the riverbed and identify clogged sections.

The Delhi government will undertake topographic and bathymetric surveys of the entire 48-km Yamuna stretch from Palla at the Delhi-Haryana border to Jaitpur at the Delhi-Uttar Pradesh border to map the riverbed, identify clogged sections and assess changes in the river’s course, senior government officials said.

The Yamuna survey from Palla to Jaitpur will map underwater terrain, river course changes and physical features to aid flood management in Delhi. (HT Archive)

A Bathymetric survey measures water depth and maps the three-dimensional shape and contours of underwater terrain. It functions as an underwater equivalent to a land topographic survey.

The surveys will also map embankments, spurs, drains, islands, encroachments and ghats within 100 metres of either bank, with the findings expected to aid flood management as well as planned riverfront development and boat navigation activities, officials said.

Besides improving flood management, the government plans to undertake riverfront development projects and boat navigation activities in the river channel, with the survey findings helping in the planning, officials said.

The Irrigation and Flood Control (I&FC) department invited bids on October 1 to undertake two types of surveys of the river from Palla to Jaitpur. “The bathymetric survey of the Yamuna will cover the entire 48km river course in Delhi. The exercise will undertake cross-sections of the river at every 250m interval. The topographical survey will also develop the contour plan of the river, identify changes in the river’s course and its topography. Both surveys will involve the use of electronic total station machines, echo sounders and sonar systems mounted on motorboats,” an official explained.

A topographical survey is an assessment of a site’s physical characteristics, including its natural and man-made features and their elevations, to create a comprehensive map. A bathymetric survey maps the underwater terrain by measuring water depths and can be crucial for understanding the riverbed’s condition and for future drainage and riverfront development projects. It maps the underwater terrain, much like a topographic survey maps the land’s surface.

“The survey uses technologies like single-beam and multi-beam sonar, acoustic Dopplers, GPS and motion sensors mounted on a boat to map the bed as it passes along the water channel. The sound velocity data and sensor data are fed into software to get a digital map of the surface,” the official said.

The Yamuna surveys are likely to cost around ₹80 lakh, and the agency will be given eight months to complete the exercise.

Last year, the Delhi government had stated that it intended to undertake the first dredging of the Yamuna riverbed, for which it would approach the National Green Tribunal. The proposal was aimed at reviving the river’s natural flow, easing pressure on regulator drains and enhancing flood resilience in low-lying neighbourhoods along its banks. Dredging is an exercise usually done for smaller water bodies such as canals and lakes and involves the excavation of accumulated silt, sludge and solid waste from the riverbed.