護岸 is read as ごがん (gogan) and means river dike.
ごがん
gogan
ごがんこうじ
levee protection works
ごこく
defense of one's country
ごけん
protecting the constitution
ごえい
guard
ごそう
escort (e.g. under guard)
ごしん
self-protection
ごじ
defend and maintain
ごみんかん
tribune (of ancient Rome)
ごほう
defence of the constitution
ごしんよう
(for) self-defense
ごきょうろん
apologetics
ごそうせんだんほうしき
convoy system