Bosphorus

The Bosphorus is one of two Turkish Straits that separate Europe from Asia, the other is the Dardanelles.
The Bosphorus is an 18 mile (30 km) stretch of water flowing past Istanbul and connecting the Black Sea with the Sea of Marmara.

It is between 160-330 ft (50-110 m) deep, and at its narrowest point it is only 2,300 ft (700m) wide and is S-shaped.
As it is the point where Europe meets Asia, many Armies and Migrations have crossed the Bosphorus in both directions.
In 513 BCE, the Persian Emperor Darius I, built the first bridge across the Bosphorus. It was a Pontoon Bridge of 720 vessels roped together, and he sent his armies over it to invade Greece.
In 270 BCE, three Celtic Tribes from Gaul crossed the Bosphorus and invaded Galatia, later founding the Kingdom of Galatia.

A city has been here for two and a half thousand years, because of its strategic location between two continents, its location for east-west trade, and rich fishing grounds.
657 BCE – 326 CE The Greek City of Byzantium was founded and built here.

In 326 CE Constantine I renamed Byzantium ‘Roma Nova’ and it was eventually called Constantinople.
It became the Capital of the Eastern Roman Empire which later became the Byzantine Empire. It also was on the Silk Road from China. The Byzantine Navy was based here in the estuary Harbour of the ‘Golden Horn’, protected by a chain across the river mouth.

In 1453 CE Constantinople was renamed Istanbul after the Ottoman Turks captured it, and it became the capital of the Ottoman Empire.

The Bosphorus narrows to 0.38 nautical mile (700m) between Kandilli Point and Asiyan.
At Kandilli Point, the normal Current of 3-4 knots can flow at up to 7-8 knots.
To pass this point, ships must turn through 45 degrees.
Further south at Yenikoy, ships must again turn through 80 degrees.
Whilst negotiating these turns Ships cannot see ahead or behind, and cannot see each other, increasing the chances of a collision.
Today, a one way system has been imposed. Northerly traffic passes the Strait between 00.00 hrs and 11.59 hrs., and Southerly traffic passes between 12.00 hrs and 23.59 hrs.
To avoid the strong current in the Bosphorus, ships can stay near the coastline on either shore, where the current is weaker or can reverse. However, the shallow waters impose a danger of running aground.
Sailing at night would have been too hazardous for ships in the ancient world.

The Prevailing Winds are northerlies, making progress against the Wind and Current very difficult.
The Northerlies tend to funnel through the S-Bend producing winds of between 20-25 knots.

The surface current flows south at a rate of 3-4 knots, from the Black Sea to the Sea of Marmara. However, the current is weaker along the coastlines.

Underneath the surface current, is another current which flows in the reverse direction.
This makes it perfect for fish to migrate in both directions. As a result, during the migration period, the Bosphorus produces superb fishing grounds, and has done since Antiquity.

Bosphorus