The problem is that many or all good sites for settlements lie on a shore or along a river. Add to that that in the erly middle ages, transport by ship was far superior to any land based transport. An early medieval society battling Draugr would need to radically change it's relationship to open water bodies. 878
If you feel my answer assumes to many or too powerful Draugr, tone down the responses - only some are follwed at some places etc.
Draugr attack methods:
* attack boats from below with grappling hooks, trying to capsize them
* Sneak attack on villatges by the sea
* Hiding in boats left on shore
* sabotaging boats left on shore
* March up rivers to attack towns further inland, along shores of rivers and lakes
* Ambush in rivers at major fords, attack bridges to force the use of fording
Defenses and second order effects:
* Don't build enclosed harbors, instead have fortifications with a wall between the shore and the houses
* Every night, drag boats into the walled settlements (this would apply to fishing villages and the likes)
* When this is not possible, each new day for sailors and fishers will begin with a ritual check of their vessels for hidden Draugr (possibly with dogs) and sabotage traces
* Naval architecture 1: I guess a boat shape that is well suited to drag across a beach twice a day would be flat bottomed and fairly light, which would be susceptible capsizing by attacks from below. So maybe the go-to boat for fishers will be a sort of light catamaran, as a good compromise of stability and lightness.
* Naval architecture 2: Build boats so heavy and stable, with so much draft and such high boards, they can't be capsized by grappling hook attack from below. These will of course not be dragged on shore. Since a few patient Draugrs with drills could sink one on the high seas, I don't see much high sea travels.
* rafting timber or other goods along rivers will be a thing for the reckless, as will be crossing rivers through fords
* The uselessness of rivers for transport will force the societies to use more road based transport, at some distance from the cities.
* Rivers will be even stronger borders than before 87