Channel Bottom Levels

For an Inner Channel required depth/draught ratios are based on the following criteria, from table 2.2 of the PIANC guidelines. The vessel speed is calculated by adding the longitudinal current to the absolute vessel speed which has been defined by the user.

Vessel Speed (knots)	Min. depth/draught ratio
<10 knots	1.1
10-15 knots	1.12
>15 knots	1.15

Whereas for an outer channel the minimum depth/draught ratios are based on the following criteria, also based on table 2.2 of the PIANC guidelines (guidelines values are in black, values used by software are highlighted).

Swell Height (m)	Min. depth/draught ratio
Hs < 1m	1.15 - 1.2 (1.2)
1m < Hs < 2m	1.2 - 1.3 (1.3)
Hs > 2m	1.3 - 1.4 (1.4)

In additional to these minimum depth/draught ratios, the following values are also added for the channel bottom type, from table 2.2 of the PIANC guidelines.

Bottom Type	Inner Channel	Outer Channel
Mud	0.0m	0.0m
Sand / Clay	0.4m	0.5m
Rock / Coral	0.6m	1.0m

Finally, the following addition to the channel depth is also made for rolling if the vessel is a container ship or car carrier, based on section 2.3.2 of the PIANC guidelines.

The total channel depth for each design vessel is calculated as follows:

Total Channel Depth = Vessel Draught x Min. depth/draught ratio + Additional depth

For each design vessel the minimum channel bottom level is calculated as follows:

Min. bottom level = Transit water level - Total Channel Depth