X-band persistent SAR interferometry for surface subsidence detection in Rudrapur City, India

Urban areas due to their dynamic nature often pose serious threats to environment causing overutilization of resources like ground water. The depleting ground water table often causes land subsidence leading to cracks in buildings. This subsidence can be easily mapped using PSInSAR (Persistent Interferometric Synthetic Aperture RADAR). In urban areas, there are many buildings per square kilometer which give permanent scatter and act as good corner reflectors at boundaries right angle to ground and walls. Rudrapur city, which is the headquarters, of Udham Singh Nagar district of Uttarakhand state in India, is also a major industrial hub and attracts skilled and unskilled labour force from the adjoining areas and this is leading to an unprecedented growth of urban sprawl. The city shows sprawling dense urban settlements and huge industrial setups on the outskirts, surrounded by agricultural fields and orchards. Main source of water supply is through bore wells and tube wells. Here, it was found that over the years, ground water has been harnessed for not only household supplies but also for agriculture and industrial purposes which has led to lowering of water table down from around 33.5 m to 45.7 m. This is leading to cracks developing in buildings particularly around the industrial area. The changes over a period of a year from 4th December 2014 till 2nd December 2015, were mapped using PSInSAR technique, with X-band TerraSAR-X datasets.