GEO Research

Mapping of High Tide Line

The coastal regulation zone (CRZ) are decided on the basis of High Tide line (HTL).

The High Tide Line (HTL) is defined ‘for the purpose of the CRZ notification’ as “the line on the land upto which the highest waterline reaches during the spring tide”. The HTL along with CRZ notification are the prime factors followed to govern the coastal zone of the country. Any violation within the HTL and CRZ are legally punishable. NCSCM has completed the demarcation of HTL for the entire country using aerial photo of 2011 of 9cm resolution. The HTL is identified based on geomorphologic features and other features such as embankments, landward boundaries of sea wall, tidal flats, mangroves, etc (MoEF & CC, 2011) and where ever aerial photographs are not available high resolution satellite images such as Quick Bird, IKONOS, Worldview are used for the extraction of HTL.

The High Tide Line forms the cardinal reference line for determining the setbacks for CRZ. The 100, 200 and 500m CRZ lines landward from the HTL are the landward setback lines. The Low Tide Line (LTL) and the Territorial water boundary (12nm) form the setback lines towards the sea. The CRZ maps are prepared in 1:4000 scale with superimposing the proposed activity/layout plan for the use of local bodies and other agencies to facilitate implementation of the CZMPs.