Reservoir and river ranges are routinely underestimated. Choose the wrong mooring and the bridge grounds in the dry season and breaks loose in the wet.
Mooring falls into three families: pile guides, guide chains with counterweights, and shore-side hinges. Below 1.5 m of range, pile guides are the most economical; beyond 3 m, chains and counterweights are usually required.
We check both extremes: does the deck ground at minimum level, and does the chain angle exceed design at maximum level. Calculating only the mean level is a common mistake.
Above 8 m of range, abandon a single mooring method — use long guide chains with adjustable tensioners, and write the annual inspection items into the O&M manual.