Obviously a river flows in one direction. Any tidal river I assume does the same thing. The Potomac river for example (tidal portion): what happens to the flow when the tide is incoming? I know the river doesn’t reverse flow, or does it, in some layered fashion? How else can you account for 2-4 foot tidal differences. One of you scientific paddlers must have the answer.
tide velocity
moon phase greatly influences velocity of tides and yes, river outflow can be overcome by a strong incoming tides ,essentially stalling outflow…but think of it as more of the water rising in a localized area and bulging upwards, and yes they can occur in “layers” this space is much too small to fully discuss tidal hydrodynamics and the various influencing factors.
Not dumb at all
Rivers most definitely can reverse under tidal pressure, here’s a good example: http://www.paddling.net/places/showReport.html?252
I live on a tidal river about 12km from the ocean, and watch the tide travel upriver twice daily. Although not nearly as dramatic as the Salmon River bore mentioned in the above article, the tidal flow is a great aid to covering distance if you time your trip properly.
I posted a similar thread…
…ten days ago, look on page 6. I suppose every body of water has its own characteristics. If the tide change is only a few feet, you might not notice any current at all, or maybe just a little at peak change times.
And, yes, its amazing how wind can push water enough to actually raise the level in spots.
Estuary
a river that flows out to the sea(so any fresh water that flows into salt) and is affected by the sea ebb and flood . There are many ! In the NE the Hudson (Muhheakkunnuk-water that flows both ways ), Connecticut , Cape Fear in NC , just to name a few. The Hudson has a tidal difference in Albany 150 miles upstream . Depending on where and what sort o flow and moon and wind and bottom contours as well as the sides of the river can make any tide predictions "seem wrong " . Saltwater will roll up like a cartoon tounge . Other helpful info from tide charts are slack before flood , maximum flood etc… check it out pretty flippin interestin , impress yer friends !
My local river flows both ways
There is alway fresh water heading to the sea, but the sea pushes pretty far back up each cycle. My small side canal is more salt than fresh - except after VERY heavy rains.
Salinity/density differences (it doens’t mix all that quick) in the river create some interesting things as the fresh can overrun the salt and have water going both directions atthe same time. Also creates eddies both horizontal and vertical.
Slow enough river, and small, so flow is not dramantic going either way.
ON a good day
You can get whirlpools at the mouth of the essex river. might want to have your game on. That is the outfowing water strugging with the incoming water. Even a few miles in from the ocean you will see over 5 foot tidal changes. That water comes from the ocean.