Hydrographic Surveys and Routing Measures:


“…Mindful of the special hydrographic and ecological characteristics of the marine environment of the Red Sea and Gulf of Aden and the particular vulnerability of its coral reefs where most biota exist…”  (Jeddah Convention, Introduction)




In 1996/98, preparatory research was carried out by Det Norske Veritas (DNV) for the World Bank that recommended the establishment of new traffic separation schemes to separate northbound and southbound streams of traffic throughout the Red Sea. Regional experts reviewed the DNV report and considered that a number of smaller schemes would overcome technical difficulties with the DNV proposals, but would achieve the same objective.

Proposals were made in 1999 to establish new routing measures in the southern end of the Red Sea to control traffic operating between Bab el Mandeb and the restricted passages lying east and west of the Hanish Islands – an area used by around 20,000 ships per year. Routing measures already control the movement of ships along the whole length of the Gulf of Suez and the measures in the southern Red Sea were planned to provide similar control at the other end of this vital international waterway.

The measures proposed for the southern Red Sea extended over a total distance of some 150 nautical miles and covered an area of 750 km2. The first requirement was to conduct a hydrographic survey of the area, as a survey to the modern standards set out by the International Hydrographic Organization (IHO) in Document S-44 is a pre-requisite before routing measures of this kind can be adopted by IMO. Previous surveys of this area were largely conducted in the 1860’s to 1880’s using outdated survey methods and supplemented by depth reports from ships on passage, which are not sufficiently accurate for the adoption of routing measures.

Planning and Process:

The first meeting of the Navigation Working Group validated the preliminary design of these measures in April 2000. During 2000 PERSGA and the World Bank prepared a consultancy services contract between PERSGA and the UK Hydrographic Office and then initiated an international tendering process, through which a contract with Gardline Surveys for the hydrographic surveys was bid and let.

At the April 2000 NWG workshop, the UKHO agreed to re-scheme charts of the southern Red Sea in order to achieve a more satisfactory chart coverage for navigators and improve the safety of navigation. In July 2000 Yemen, Eritrea and Djibouti submitted a request to the IMO Subcommittee on the Safety of Navigation to advise on whether PERSGA should proceed. The Subcommittee was unusually positive in its confirmation and highly commended the preliminary work that had been carried out. The decision to proceed with the survey was made with a fair degree of confidence that the measures would eventually be adopted by IMO.

The process through which the hydrographic surveys were conducted is summarized in the following table:




PERSGA/UKHO contract terms agreed and contract signed

February 2000

IMO Navigation Sub-Committee considered draft routing measures and recommends that PERSGA should proceed with the survey on the basis of these proposals

July 2000

PERSGA/Gardline Surveys contract terms agreed

September 2000

Survey vessel ‘Ocean Seeker’ leaves Europe for Red Sea

November 2000

Survey vessel mobilized in Aden - survey programme starts

December 2000

Survey conducted and completed – monitored at all stages by SAP and UKHO (in spite of unusually adverse weather in the area)

January 2001 to June 2001

Survey results presented to second NWG workshop in Djibouti for discussion

July 2001

Gardline submits survey data to UKHO for validation

August 31st 2001

Survey data fully accepted and approved by UKHO

Dec 15th 2001

New re-schemed charts on sale to international shipping through chart agents (showing the area surveyed by PERSGA in 2001, but not the proposed new routing measures)

Feb 28th 2002

As part of the hydrographic survey, accurate current and tidal measurements were made at several points in the region to enhance the body of knowledge on regional currents and tides. Samples of the sea bed were also taken at an interval of 1km2 throughout the survey. Under the contract with Gardline, 90% of these samples were sent to the University of Sana’a, and 10% were sent to the UK Hydrographic Office for analysis.

The survey clearly demonstrated that the underwater topography between the Hanish Islands and the southern side of Bab el Mandeb is safe for the introduction of the proposed routing measures. Because of the importance, complexity and the size of the area covered by this survey, UKHO, the largest charting organization in the world, had to review its survey validation processes and develop new computer methods for handling the amount of data collected. PERSGA has therefore been directly responsible for bringing about improvements to international validation methods for hydrographic surveys, a result that could not be predicted when the SAP was first planned and initiated.

Survey Report:

After completing the survey in the southern Red Sea, the process of submitting the proposed routing measures for adoption by IMO continued, as shown in the following table:




Draft charts showing the proposed routing measures produced by UKHO

February 2002

Draft charts approved by NWG

March 2002

Detailed description of routing measures prepared and sent with charts to Eritrea and Djibouti requesting letters of support for a submission to IMO

March 2002

Routing measures sent to IMO for submission to the Nav. Sub-Committee

5 April 2002

Routing measures considered by IMO Subcommittee on the Safety of Navigation and sent to the IMO Maritime Safety Committee (MSC) with a recommendation that they be adopted by the Organization

8 July 2002

Routing measures considered by MSC and adopted by IMO

December 2002

UKHO published 7 re-schemed navigational charts of the area showing the new routing measures – charts on sale to international shipping

May 2003


The new routing measures entered into force for international shipping
Midnight 1 July 2003

IMO Ships’ Routing Book updated

End 2003

Annual Summary of Notices to Mariners describing the new routing measures in the southern Red Sea published

End 2003

 PERSGA required the Avocet Rock to be included in the survey, although this lies outside the area of the routing measures. The Rock is important, as it lies only 6 miles east of one of the main routes and is a dangerous navigational hazard. Following the survey it is now known to consist of an unmarked plateau of rock around 6m below sea level that extends 400m by 400m horizontally. It has caused a number of shipwrecks since the 1870’s and was fully surveyed for the first time during the PERSGA survey. Other shallow patches that had been reported by ships on passage, lying southwest of the Hanish islands and south of Bab el Mandeb close to the proposed measures, were disproved.
Outline plans have been prepared for extending the separation of traffic in the Red Sea all the way along the 1,100 mile route from Bab el Mandeb to the Strait of Gubal. With routing measures now established at each end, it will be relatively simple and inexpensive to secure the adoption of measures to provide a separation of at least five miles between northbound and southbound traffic flows and eliminate the present 500,000 potentially hazardous ‘end on’ meetings of ships each year in the Red Sea.