I have discussed this topic before and am interested in hearing your thoughts...I have always been interested in waves breaking where they shouldnt, ie:small rivers, even lakes...take the assawoman bay or the choptank river...I live on the choptank river, how possible would it be for waves to break there? Is it possible? I know waves have been ridden on the chesepeake bay...
. . . there are several ways for waves to show up in atypical areas like bays and rivers:
1) Wind on water over a considerable distance (fetch) and over time wherein the energy of the wind is transferred to the water first creating ripples, and then ripples upon ripples. Oceans are more amenable to these waves first because they have the fetch (size), second because they have the depth to allow free movement of the transferred energy, and third because they allow winds free reign once generated by pressure and temperature differentials.
2) Tidal Bores, where rivers at generally extreme lattitudes can get a wave that travels up from the mouth of the river (as in surfer Rodney Sumpter riding river waves in Nova Scotia). Basically it's the extremes in tides (as much as 30 feet or more) in the extreme lattitudes that cause the waves. The tidal cycle is still around 6 hours, but the extreme inflow is what can literally create a recognizable wave moving upstream.
3) Refracted swell energy- when it gets really big in the ocean, some of that wave energy can make it into an inlet and refract off the jetties all the way into the bay where all it needs is some shallow water like a sandbar to produce a breaking wave, although the size is greatly diminished. Even here, the waves are still affected by wind direction and velocity. Back Bays can also generate their own internal waves (very short period) given enough velocity, fetch and duration. Great Lakes waves have been known to sink ships like the Edmund Fitzgerald.
4) Standing Waves- rivers that have rapids can form standing waves over large boulders, much like a FlowRider does-
. . .and of course there are a multitude of others like boat wake, wave pools, et al. where displacement of water creates the wave either from a boat or from pumping water up into a wall and then releasing it as Typhoon Lagoon does at Disney.
Obviously, some waves are more ridable than others.
i often have dreams of surfing the most obscure places, none of which are in the oceans.
The chances of you surfing a wave in the choptank river is not likely. Unless, you dug out a trench, and created a standing wave when you had enough current moving.
MDSurfer explained things pretty well. For wind produced waves, the ones we generally ride, you need wind blowing over the water.
There are 3 variables that are directly proportional with an increase in wave height:
wind fetch (area covered)
increasing anyone of those variables will increase your wave height. There is no room in the river you are referring to for any wind fetch, and thus no room for swell production.
If a particular coast is exposed to the swell direction without barriers than it will see swell energy. The ocean bottom contour is the tricky part of the equation, as it can contribute to swell being refracted or defracted (meaning the waves bend towards or away from the coast respectively). The refraction process is responsible for swell sneaking into unexposed areas.
3) Refracted swell energy- when it gets really big in the ocean, some of that wave energy can make it into an inlet and refract off the jetties all the way into the bay where all it needs is some shallow water like a sandbar to produce a breaking wave, although the size is greatly diminished. Even here, the waves are still affected by wind direction and velocity. Back Bays can also generate their own internal waves (very short period) given enough velocity, fetch and duration. Lake Erie waves have been known to sink ships like the Edmund Fitzgerald.
Now thats some pretty serious refraction if Lake Erie waves made it all the way up into Lake Superior where the EF sank.
dog beach in manasquan inlet can get really good for a longboard with lefts that peel for about 200 yards, there is a shoal in barnegat inlet that breaks up to chest high but it's in the middle of the inlet the currents are wicked and its a long paddle, or in the winter and spring when the wind is really hard west, the west side of cape may on the delaware bay is rideable with 1-3 foot onshore chop, there are jetties that can jack the waves up enough and the better breaks are within a mile or two of the ferry, too far north and the bottom gets too flat, surfed in january one year with a quad and it was actually ripable BUT it was 35 degrees out with a 35mph west wind in my face, i also share the interest in unusual waves and I have dreams about perfect barnegat bay all the time