Why can you ride a flood but not an ebb?

Going from San Francisco to Stockton or Sacramento, one can ride the flood current the whole way. However, on the return trip, one cannot ride the ebb the whole way. Why not?

Both the flood tide and the ebb tide begin in the ocean, and both move north through San Pablo Bay and up the Sacramento and San Joaquin Rivers. While the max current will typically be 2 to 3 knots, the wave that is the max current (or high tide, or low tide, or ...) travels at between 7 and 13 knots. Therefore, if you boat's speed through the water is approximately 7 knots, you can ride the max current for many hours up the bay and river.

However, the ebb current also moves north through the bay and up the rivers. Therefore, if you start up in the delta at max ebb, and sail down the river, you will soon be sailing into the tail of the ebb, and then into the slack, and then into a flood.

The better approach is to start down river at the beginning of the ebb and stop for the night at the tail of the ebb. Alternatively, plan to be at the points of the fastest current during the ebb.

Examples of the Speed of the Tide Wave

Below are two tables. One follows high tide up the San Joaquin and the other follow low tide along the same path. The locations are tide stations along the route. For each, the time of the high/low tide is taken from a tide chart and the distance is taken from Navionics Auto Route. The time for the "wave" to move from tide station to tide station is calculated and, from that and the distance, the speed of the wave is calculated for each leg. The average speed of the high tide wave was 10 knots. The average speed of the low tide wave was 9 knots. But the speed of the wave will vary based on the height of the low and high tides.