Nattavgangen går uansett om bølgehøyden er høy eller lav.

Because Norwegian usually writes compound nouns as a single word.

Here, nattavgangen is made up of:

• natt = night
• avgang = departure
• -en = the definite ending for a common-gender noun

So:

• en nattavgang = a night departure
• nattavgangen = the night departure

A useful rule: in Norwegian, the last part of a compound is the main noun, and that is the part that decides gender and inflection. Here the main noun is avgang, so the whole compound behaves like avgang.

Yes, går often means goes or walks, but in transport and scheduling it is very commonly used to mean:

• runs
• operates
• departs
• is in service

So in sentences about buses, ferries, trains, or departures, går often has this timetable meaning.

Examples:

• Bussen går klokka 8. = The bus leaves at 8.
• Ferga går hver dag. = The ferry runs every day.

So in your sentence, går is not about physically walking. It means that the night departure still operates.

Uansett om means regardless of whether.

It is a very useful expression:

• uansett = regardless / anyway / in any case
• uansett om ... = regardless of whether ...

So the clause after om gives the thing that does not affect the result.

Examples:

• Jeg drar uansett om det regner. = I’m going regardless of whether it rains.
• Kurset holdes uansett om få møter opp. = The course will be held regardless of whether few people show up.

In your sentence, it means the departure operates no matter which of the two possibilities is true.

Here, om is closer to whether than to if.

Norwegian om can mean different things in different contexts, including:

• about
• if
• whether

In this sentence, it introduces an indirect yes/no-type choice, so whether is the best English match:

• om bølgehøyden er høy eller lav = whether the wave height is high or low

A helpful comparison:

• Hvis is often used for real conditions: If X happens, then Y
• Om is often used for whether

So here uansett om is much more like regardless of whether than regardless if.

Because om introduces a subordinate clause, and in Norwegian subordinate clauses the word order is usually subject + verb.

So you get:

• om bølgehøyden er høy
  not
• om er bølgehøyden høy

Compare:

• Direct question: Er bølgehøyden høy? = Is the wave height high?
• Indirect clause: ... om bølgehøyden er høy = ... whether the wave height is high

This is a very common pattern in Norwegian: direct question word order changes when the question becomes embedded inside a larger sentence.

Because bølgehøyden is the definite form: the wave height.

It is also a compound noun:

• bølge = wave
• høyde = height
• bølgehøyde = wave height
• bølgehøyden = the wave height

The sentence is talking about the specific wave height relevant to this departure or route, so the definite form sounds natural.

Compare:

• Bølgehøyde kan være viktig. = Wave height can be important.
  
  • general, indefinite
• Bølgehøyden er høy i dag. = The wave height is high today.
  
  • specific, definite

Because they are predicate adjectives, meaning they come after er and describe the subject.

In Norwegian, predicate adjectives usually agree with gender and number, but not with definiteness in the same way attributive adjectives do.

Here:

• bølgehøyden is singular
• the head noun høyde is a common-gender noun
• so the adjective stays in its basic singular common-gender form:
  • høy
  • lav

Compare:

• Bølgehøyden er høy. = The wave height is high.
• Huset er høyt. = The house is high/tall.
  
  • neuter noun, so høyt
• Bølgene er høye. = The waves are high.
  
  • plural, so høye

So høy eller lav is exactly what you would expect with a singular common-gender noun.

Because one er can apply to both adjectives when they are linked by eller.

So:

• bølgehøyden er høy eller lav

works the same way as English:

• the wave height is high or low

Repeating the verb would be grammatically possible in some contexts, but unnecessary here. Norwegian usually avoids repeating it when the structure is clear.

Because Norwegian main clauses usually follow the verb-second rule.

That means the finite verb normally comes early in the sentence, usually in position 2:

• Nattavgangen = first element
• går = finite verb in second position
• uansett = adverb after the verb

So the structure is:

• Nattavgangen går uansett ...

This is very typical Norwegian word order.

If you moved things around, the verb would still need to stay in second position:

• Uansett går nattavgangen ...

That version is also possible in some contexts, but it changes the emphasis. The original sentence is the more neutral way to say it.