River seamanship


Since many rivers are tidal and are regularly navigated by vessels coming from the sea, the title of this section is not, in fact, a contradiction. Rivers carry their own challenges, and specific techniques are required for their ready negotiation. Some rivers are fully charted, but the fact that many are not is no reason for refusing to explore them. If navigable within the limits of most users, a pilot book will generally offer enough data to proceed.


Collision regulations


Tidal rivers are often subject to local byelaws, particularly speed limits. If you are in doubt as to what these may be, proceed at a sensible speed – slower rather than faster – leaving no unnecessary wash. Generally, speaking, the International Regulations for Prevention of Collision at Sea (COLREGS) apply in rivers as far as their connection with tidal waters remains uninterrupted. For example, they cease at the first lock gate, if there is one. Thereafter, the regulations may still be adopted, but local, national or continental byelaws could well modify or augment them, such as the European CEVNI regulations for inland waterways.


Tidal considerations Height If in doubt, enter a tidal river around half-flood, then proceed with caution knowing that, should you run aground, the rising tide will lift you off. Navigating a strange river on a falling tide is strongly discouraged. Springs/Neaps While arriving at High Water, Springs appears to have much to recommend it, to run aground on top of a big tide can be disastrous. If the next High Water is lower and you have failed to get off, you are condemned to wait for the next spring tide, which may be a fortnight or much more away. This unhappy state of affairs is called being ‘neaped’.


Controlling depth When entering a river whose depths are uncertain, note your exact track and keep an eye on the sounder. Record the shoalest point. Once inside, you can reduce this controlling depth to soundings and be sure that on that line at least you know what the depth will be as you return to the sea.


140 | MANUAL OF SEAMANSHIP


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