No. Jabez is far upstream and not impacted by this.Goose,
What was the bottom's composition and structure before the silting? I don't know. Presumably, at least in the last few thousand years, the delta-nature of that area always made the bottom somewhat muddy/sandy. Interestingly, the shore around Indian Landing is once again failry hard/sandy, with a ton of clam shells. I have no idea why it's that way now. I am aware of no SAV until you get well up into the actual Run, however.
Are these the same areas that I have heard legendary talk of the Yellow Perch runs? Yes. And significant Y (and W) Perch runs still occur...they may even be getting modestly better. I do not know precisely what caused the reduction of these runs (starting in about the late-70s, I guess)....there so many possible culprits that it's hard to point the finger at any one thing, but toxins trapped in the mud are certaionly one strong possibility. Unless all of the mud is dredged out (a gigantic, ultra-expensive task), I don't see that changing.
Is this silting-in one of the reasons for their demise?
What has been done in the watershed to help alleviate the silting issues? Well, not much from an active point of view. From a passive standpoint, contruction of Rt. 97, combined with the construction and massive deforestation of the Shipley's Choice community, are often identified as the primary culprits and that construction has long-since stopped. However, that part of the Severn was still very muddy before that. I suspect that construction projects throughout the Severn Run watershed all contributed over time. Very little concstruction occured between about 86' and about 2000, and I haven't noticed much of a change in water depth over that time, but in the last several years we've seen another min-building boom in that area. My hope is that tighter stormwater restrictions are keeping the inflow of silt to much lower levels than in the past.
And, are these issues part of the Jabez Branch stuff?