Hmmm...Hip roof...hate to disagree , but a hip roof slopes on all four sides, looks more like a Gable roof to me.
From the actual bridge photo, the vertical wall at the entrance is only vertical half way up then slopes out to provide a bigger over hanging Gable at the the bridge entrance, hope that is understandable.

.
Looks like a great relief carving is well on it's way.

.
OG