There are three problem areas on the petaluma river.
first is 2000 feet west of the green channel marker in the river (There is only one). Note this is a gravel bottom and not soft. (Don't ask me how I know), from mid river to the south (101) side by the side canel (see photo) is 4' at mean low water
. Hold to the north side of the river which is 8' deep at MLW.
Second is at the new green railroad bridge at haystack landing. The old swing bridge was only 1/2 the width of the new bridge. As the new green span is twice as long it made the river wider. But from mid river to the south side is still un dredged and silted in. Hold to the north (marina) side of the channel there.
Third, there is a shallow spot in the middle of the turning basin that you will find at low tide.
Added bonus, The petaluma marina has a silting issue and only has 36" of water
in the fairways at MLW and 4' at the river entrance at MLW. You will want to enter and leave at other then low tide.
Crossing San Pablo in the afternoon with an outgoing tide in a 24 foot boat can be exciting. I try to cross it from the petaluma river in the morning before the after noon winds come up.