The river flowing backwards in Wisbech

 

We were amazed to see the River Nene flowing the wrong way in Wisbech and then realised that although we were 10 miles inland, it was the tide. I'm told that spring tides with a strong wind to hold it can fill the river to the bottom of the bridge. I was wondering what affects the distance to which the tide flows inland. I found this https://en.wikipedia.org/wiki/Head_of_tide I went looking for the Normal Tidal Limit of the River Nene and found out that it is at least as far inland again, almost to Peterborough, at Dog in a Doublet https://www.waterways.org.uk/waterways/canals_rivers/river_nene/river_nene As yet, I cannot find anything on what factors affect the placing of the Normal Tidal Limit NTL on a river. A wider river would have more water from the sea moving in but a narrower river would possibly "squeeze" it more to get it further.