I think the old SciFi classic "Zone of Thought" and the other book which name escapes me now explorer this idea, although not 5Km/h.
To stop a 'blight' in the universe, some natural laws have to be changed wherever it starts to spread, is the story premise if memory serves me.
"A Fire Upon the Deep" and "a Deepness in the Sky" by Vernor Vinge
The third volume of « Three body problem » and its fan-written and author-approved sequel deal with those local physical constants changes !