5 ms·
Geologist here: while overly managing of the Mississippi does make a difference, that only controls where new sediment gets deposited. Even if new sediment was
by cossatot 9y ago
Geologist here: while overly managing of the Mississippi does make a difference, that only controls where new sediment gets deposited. Even if new sediment was deposited in sinking urban areas, it wouldn’t ameliorate the problem of subsidence because it would be deposited on existing infrastructure, burying it.
The real reason for the subsidence is that the sediment that makes up river deltas slowly compacts under its own weight, expelling pore water and becoming more dense. This is natural and unavoidable, although it might be marginally enhanced by oil and gas extraction (it is a bigger problem with groundwater withdrawal in other areas).
- specialist 9y agoYou’re the expert, but I thought subsidence (land sinking because of fossil fuel extraction) and compaction were two different phenomemons. Plus erosion (loss of coastline) and rising ocean, there’s multiple factors involved.
- cossatot 9y agoThey are related phenomena. Basically, sand and mud have pore space in between the grains that is filled with fluids (water, oil or gas). When those fluids are extracted, the rock contracts because the pore pressure decreases, causing an increase in density (compaction) and a decrease in volume, which leads to subsidence. Some of this is recoverable, and some of it isn't, because the grains will find a more efficient packing arrangement. You are completely correct in that there are many different factors involved that are all causing problems; unfortunately they are all interrelated.