The High Tide Line, the Low Tide Line and the Hazard Line

In one line

Every distance in coastal law is measured from a line drawn on a map, and three different lines matter.

In the wording a student can write in an examination: for the purposes of the Coastal Regulation Zone Notification 2019 the High Tide Line means the line on the land up to which the highest water line reaches during the spring tide, as demarcated by the National Centre for Sustainable Coastal Management in accordance with the laid down procedures and made available to the coastal States and Union territories; the intertidal zone is the land area between the High Tide Line and the Low Tide Line; and the hazard line is a line demarcated by the Survey of India taking into account the extent of flooding on the land area due to water level fluctuations, sea level rise and shoreline changes occurring over a period of time, which is to be used as a tool for the disaster management plan for the coastal environment including the planning of adaptive and mitigation measures, and not as a regulatory boundary.

Why the lines decide everything

The notification prohibits activities within the zone and regulates activities at stated distances: twenty metres, fifty metres, two hundred metres and five hundred metres. Every one of those distances is measured landward from the High Tide Line.

So the single question that decides whether a plot is regulated, and how heavily, is where the High Tide Line runs. Not what is built, not what is discharged, and not what harm is caused. Where the line is.

The High Tide Line

The definition. The line on the land up to which the highest water line reaches during the spring tide.

Who demarcates it. The National Centre for Sustainable Coastal Management, in accordance with the laid down procedures, and its demarcation is made available to the coastal States and Union territories.

Its authority. The notification's annexure on the preparation of management plans provides that the demarcation carried out by that Centre for the entire coastline of the country has been made available to the coastal States and Union territories, and that only such demarcation shall be applicable for all purposes of the notification.

That sentence settles a very large number of disputes. Before it, the demarcation was done by a variety of agencies and a developer could produce one line and an objector another. Now there is one authoritative demarcation.

The Low Tide Line and the intertidal zone

The Low Tide Line is demarcated by the same Centre. The land between the two lines is the intertidal zone, classified as CRZ-I B, and it is where the sea and the land actually meet: the beach at low water, the mud flats, the mangroves at their seaward edge.