Sediment, Wetlands and Climate Change

Karen McGlathery. Photo credit: Virginia

Karen McGlathery at work. Photo credit: Virginia

Karen McGlathery, an environmental sciences professor at the University of Virginia who runs the Virginia Coastal Reserve Long Term Ecological Research program, is particularly taken with the study of marshes and wetlands.

Over the past century, worldwide sea levels have risen seven inches over the past century, and even faster in the Virginia Tidewater where subsidence has accelerated the rise. As noted in the new edition of “Virginia,” the UVa alumni magazine, marshes, barrier islands and oyster reefs are humans’ first line of defense against hurricanes and other violent storms.

“We know that, for millennia, marshes have kept pace with rising and falling sea levels as glaciers formed and melted,” McGlathery says. Marshes depend upon sediment flowing into the Chesapeake Bay and its tributaries to keep up with rising waters. But human activities such as dam building and shoreline hardening could change that dynamic. If the replenishment of sediment is blocked, the marshes could die as water levels rise.

But there is good news. Says McGlathery: “One thing that we’ve learned is that in Virginia, on the Eastern Shore, many of the marshes are doing very well — they have the capacity to keep up with the current rising seas.”

Bacon’s bottom line: If Virginians are going to think seriously about resilience in the face of recurrent flooding and inundation, we need to better understand the fundamentals of how wetlands adapt to rising sea levels. On the one hand, higher levels of sediment from eroding rivers and streams creates a problem for Chesapeake Bay ecosystems, and is considered to be bad thing. Strict and expensive storm-water management regulations going into effect in Virginia is aimed at cleaning up the Bay. But, ironically, sediment in the right places — in threatened marshlands — can help Bay ecosystems adapt to rising sea levels.  Is it possible that there is “good” sediment and “bad” sediment? We may need to adopt a more nuanced approach toward sediment. McGlathery’s work will prove invaluable.

— JAB

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44 responses to “Sediment, Wetlands and Climate Change

  1. Perhaps I’m not understanding but sediment does not “climb” up on top the marshes.. it settles into the bottom and one way we know this is that we have to dredge ship channels to keep them clear and we have dead zones where sediment has settled and suffocated bottom life.

    Finally – think about tides and how they cover the marshes.. and at certain times – higher tides cover many more marshes and storm surge tides – destroy marshlands and wetlands – as we have seen when storms cut across the outer banks barrier islands..

    and where do marshes that exist on the barrier islands get “sediment” anyhow?

    the idea that sediment is an antidote to rising seas … is wrong-headed “science”.

    • “… Jim’s and CJBOVAs comments which I interpreted as saying that, in essence, cleaning up the bay is wrong because it takes away sediment that could build up the wetlands.”

      Once again, Larry, you have read into my post something that is not there.

      Here’s what I wrote: ” If Virginians are going to think seriously about resilience in the face of recurrent flooding and inundation, we need to better understand the fundamentals of how wetlands adapt to rising sea levels.”

      And that’s what I meant. And that’s all I meant.

      • then you also said:

        ” On the one hand, higher levels of sediment from eroding rivers and streams creates a problem for Chesapeake Bay ecosystems, and is regulations going into effect in Virginia is aimed at cleaning up the Bay. But, considered to be bad thing. Strict and expensive storm-water management ironically, sediment in the right places — in threatened marshlands — can help Bay ecosystems adapt to rising sea levels. Is it possible that there is “good” sediment and “bad” sediment? We may need to adopt a more nuanced approach toward sediment. McGlathery’s work will prove invaluable.”

        come on Jim – isn’t it a tad disingenuous to not own the rest of what you said – which is what I was reacting to….

        you seem to be making the argument that sediment in the rivers might not be a bad thing if it helps wetlands.. right?

        let’s put this another way – you could be more explicit and not leave it vague – right?

        how about talking about what you mean about “good” and “bad”?

        if you are implying that sediment in runoff is a “good” sediment for wetlands – then are you not essentially questioning the basis for the Chesapeake Bay cleanup?

        • Ole Bacon doesn’t want to pay any taxes to control wastewater. He wants to let Henrico pave paradise and put up a parking lot with torrents of wastewater dragging along tons of sediment which causes algae blooms and dead zones. Next he’ll demand compensation from downstream communities for Henrico’s wetland restoration program (aka Wal mart parking lots).

          Jim and TMT are CINOs – conservatives in name only. They rant and rage about making people who drive pay for the cost of roads. They opine as to how suburban homeowners should pay the fully distributed costs of suburban life.

          But simply mention the possibility of a so-called rain tax to prevent half assed waster water from Henrico or Fairfax Counties wreaking havoc on downstream communities and you’ll get a wall of wailing and teeth gnashing over “big government”.

          Too funny.

  2. JAB: This is the most uplifting message I’ve read in a while, and what an appropriate day for it! Some Chesapeake Bay marshes are maintaining themselves and others are not. The marshes in Bethel Beach in Mathews are healthy and growing and those in Dorchester, MD are not. Understanding the process is essential to coastal resilience, but too often, uninformed individuals take isolated facts and recombine them into ‘theories’ as larryg has done in his comment. Sediment alone is neither good nor bad; it’s a little like Goldilocks–there has to be enough, but not too much, and there has to be flow from healthy streams to carry it, but not too much or too little. Part of the solution is stream and watershed restoration, and in some places, barrier beach replenishment is another. Karen McGlathery is to be commended for her work. It is indeed invaluable to the future of our coastal marshes.

    • @cjbova – rivers with deltas like the Mississippi will transport enormous volumes of sediment but if you read up on it – you’ll see that this actually leads to the destruction of wetlands as settles in the channels and affects water velocity and builds new channels.. it harms wetlands.. it does not build them.

      http://pubs.usgs.gov/fs/la-wetlands/
      do not have a delta system in the CBAY to start with much less the ocean-side of the Eastern Shore which has almost no river influence along hundreds of miles of shoreline -directly exposed to the ocean.

      but sediment drops out as rivers reach their mouths and become estuaries and we know this is true because we have known dead zones where sediment has killed the bottom wildlife as well as the fact that we have to continually dredge ship channels…

      here – read this:

      Harbor dredging advances in federal water bill
      Measure would allow state to continue building up bay islands

      WASHINGTON — — A measure that would allow Maryland to continue to unload huge quantities of dredging spoils on islands in the Chesapeake Bay — an effort considered critical for the port of Baltimore — won broad bipartisan support Wednesday in the ordinarily divided House of Representatives.

      The 417-3 House vote to approve an $8 billion water bill cleared the way for negotiations with the Senate on a final legislative package that state officials hope will be even more advantageous for state shipping operations.

      Without congressional authorization, the state could begin running out of room to dump the muck it dredges from bay shipping channels in as little as three years, even as Baltimore competes with other East Coast ports gearing up for an anticipated increase in trade from the widening of the Panama Canal.

      this is not helping the wetlands… it’s settling into the ship channels and has to be removed or else the harbors will become useless.

  3. here’s another report – worthy of reading -on the issue

    http://www.chesapeake.org/stac/presentations/221_Bilkovic_STAC_16Apr2013_FINAL_for%20posting.pdf

    Coastal Wetland Status and Trends in the Chesapeake Bay Watershed

    it’s saying something pretty different than the paragraph that McGlathery wrote – without any scientific data to back it up.

    and I’m sorry – when VIMS does studies – I tend to believe them.

  4. Sorry larryg, you’re comparing apples and avocadoes when you talk about the Mississippi Delta and Chesapeake Bay marshes. Try reading THE STORM–What went wrong and why during Hurricane Katrina–The inside story from one Louisiana scientist by Ivor van Heerden and Mike Bryan to get a better understanding of the differences where the Mississippi River is concerned. That book also has a wealth of information about the beneficial aspects of wetlands. Your VIMS presentation is an overview and can’t be generalized to a specific location. And there is nothing in it that is contrary to the work Karen McGlathery has done or is doing. It’s quite a leap for you to assume from brief quotes in a blog article that there is no scientific study behind those statements. If you’d checked, you’d find she was connected to more than 60 studies listed in Publications from the Coastal and Marine Ecology Lab.

    • She does appear to be a legitimate researcher, I concede and in reading other VIMs research – river sediment is identified as one of the ways that wetlands accrete…

      …… “…..“Tidal marsh plants are amazing ecosystem engineers that can raise themselves upward if they remain healthy, and especially if there is sediment in the water,” said Megonigal of the Smithsonian Environmental Research Center. “We know there are limits to this and worry those limits are changing as people change the environment.”

      Wetlands have developed several ways to build elevation to keep from drowning. Above ground, tidal flooding provides one of the biggest assists. When marshes flood during high tide, mineral sediment settles out of the water, adding new soil to the ground. It is one of the ecosystem’s most successful responses to the threat of sea-level rise. When sea-level rise accelerates and flooding occurs more often, marshes can react by building soil faster. Below ground, the growth and decay of plant roots adds organic matter—an effect that rising carbon dioxide levels seem to enhance. Even erosion can work to preserve wetlands, as sediment lost at one marsh can be deposited at another. While a particular wetland may lose ground, the total wetland area may remain unchanged.

      Pat Megonigal on SERC’s experimental wetland in Maryland. Sea level in mid-Atlantic marshes is rising at roughly 3 mm/year. So far this marsh has been able to keep pace.
      Pat Megonigal on SERC’s experimental wetland in Maryland. Sea level in mid-Atlantic marshes is rising at roughly 3 mm/year. So far this marsh has been able to keep pace. (SERC)
      But everything has a threshold. If a wetland becomes so flooded that vegetation dies off, the positive feedback loops are lost. Similarly, if sediment delivery to a wetland is cut off, that wetland can no longer build soil to outpace rising seas.

      Seawall overlooking the Lune Estuary, England. Seawalls can protect land from erosion, but they also keep marshes from migrating inland. (David Medcalf).
      Seawall overlooking the Lune Estuary, England. Seawalls can protect land behind them from erosion, but they also keep marshes from migrating inland. (David Medcalf).
      The impact of direct human behavior, not rising seas or higher CO2, has the most power to alter those thresholds, the scientists report. Groundwater withdrawal and artificial drainage can cause the land to sink, as is happening now in the Chesapeake Bay. According to the article, because of this kind of subsidence, eight of the world’s largest coastal cities are experiencing relative sea-level rise greater than climate change projections. Dams and reservoirs also prevent 20 percent of the global sediment ent load from reaching the coast. Marshes on the Yangtze River Delta in China survived relative sea-level rise of more than 50 millimeters per year since the seventh century, until the building of more than 50,000 dams since 1950 cut off their supply of sediment and sped up erosion.
      In addition to building vertically, marshes can also respond to sea-level rise by migrating landward. But, the authors note, human activities have hindered this response as well. Conventional ways of protecting coastal property, such as dykes and seawalls, keep wetlands from moving inland and create a “shoreline squeeze,” said Kirwin, the study’s lead author and a geologist at the Virginia Institute of Marine Science. Because rates of marsh-edge erosion increase with rates of sea-level rise, the authors warn that the impacts of coastal barriers will accelerate with climate change.

      “In a more natural world, we wouldn’t be worried about marshes surviving the rates of sea level rise we’re seeing today,” Kirwan said. “They would either build vertically at faster rates or else move inland to slightly higher elevations. But now we have to decide whether we’ll let them.”….”

      http://sercblog.si.edu/?p=4554

      still – there is a lot of coastal shoreline – exposed directly to the ocean that is not on a river… but quite a distance away -most of the eastern shore ocean-side fits this category.

      the biggest tributary for the CBAY is the Susquehanna which is heavily damned yet still dumps enormous loads of sediment which has to be dredged to keep the ship channel open to Baltimore.

      that dredge material is called “spoils” and normally the Army Corp has to get permission where to dump it – as opposed to using it to put on receding wetlands although I did find this:

      Thin-layer Sediment Addition of Dredge Material for Enhancing Marsh Resilience
      Prepared by the Virginia Institute of Marine Science June 2014

      it’s an interesting read also: http://goo.gl/QW0wpD

  5. cjbova – it’s water that submerges the wetlands that allows sediment to drop out on them.. those wetlands will never grow higher than the flood tides that cover them. Once they grow to the level of the tides – they stop rising.

    but none of this makes any real sense in terms of protecting inland from increasing sea levels anyhow unless you build walls – everywhere.

    Take the flood wall in Richmond – it has to be one continuous wall .. any break in that wall – will let water get behind it and flood everything behind it.

    the same is true of levies along rivers in flood… if the levee is breached – everything behind it gets flooded. You can have miles of sand dunes on the barrier islands but if water gets over one of them – all the land behind it gets flooded including the land behind other dunes.

    so no matter how high marshlands get – floods will go around them to get inland.

    I don’t think – scientists and others have fully understood all the different ways that flooding can affect us but I bet most of them will admit that unless you have a continuous high wall – that storm surges will go around the places where there are no walls.. just as they would in Richmond city.

    FEMA has actually dealt with that reality – in fact:

    “NEW FEMA FLOOD MAPS COULD MEAN INSURANCE RATE ADJUSTMENTS FOR COASTAL MARYLANDERS

    I’d actually be curious to know how or if FEMA takes into account the wetlands rising or falling for their flood maps.

  6. I’m beginning to think that either: Larry has a broken leg and can’t get out of the house; or he’s getting paid by the word by someone.

    Seriously, the civil engineers’ slogan for “storm water” is “slow it down.” Depositing sediment in growing or stable wetlands seems a good goal to me. Watching sediment through sudden erosion seems like a bad result to me.

    • TMT – what is the entire Chesapeake Bay Cleanup about?

      what do you make of Jim’s and CJBOVAs comments which I interpreted as saying that, in essence, cleaning up the bay is wrong because it takes away sediment that could build up the wetlands.

      perhaps I misunderstood but that was what I was asking…

      we spend all this time and money trying to get sediment out of the river. we even dredge the channels to get it out – and now I think I’m hearing that all that time and money is ..essentially wrong…

      clue me in.. where am I going wrong here?

  7. “I’m beginning to think that either: Larry has a broken leg and can’t get out of the house; or he’s getting paid by the word by someone.” – TMT. Funny, I was thinking the same thing, but more along the lines that his job isn’t challenging him enough 😉
    So, sediment is a good and natural process in a water system. Just as erosion is. The wetlands accept and filter sediment through turbid waters. They don’t all just sink to the bottom upon entry to the waterway. This occurs with the regularly occurring turbidity through wind, wave and tidal action and the bigger stuff gets deposited and filtered during major storm events. Since the beginning of time (presumably), wetlands have been expanding and contracting based on water level and migration of land. The wetlands also generate their own “sediment” by the decomposition of their own materials. The problem is that we settlers have unbalanced the system by dumping a gazillion tons of sediment, necessitating dredging of shipping channels and resulting in cloudy waters which inhibit plant and shellfish growth (among other things). If you look at historic maps, or read the journals of the Chesapeake’s earlier explorers (Capt. Smith to start), tall ships were going far further up rivers that we couldn’t presently conceive of anything more than traveling by dinghy. The stormwater management requirements in place around the Chesapeake are to prevent the gutting and excessive erosion of channels which dump sediment into the bay waters, as well as stemming the unfiltered flow of contaminated water into the bay. Hopefully with an increase in these devices/processes, we can allow the bay to more naturally utilize and shift all the existing sediment we’ve deposited to bring the system closer to balance. The fact that we are facing an accelerated sea level rise however, is a whole other issue that time will tell whether the wetlands can defend against. But encouraging continued human sedimentation of the waterways is certainly not the answer. Bottom line, there is “good” sediment and “bad” sediment. The good sediment is part of a natural system in balance, uninfluenced by human activities. The bad is what we excessively dump in, which is now well beyond the bay’s carrying capacity.

    • I think I’m inclined to accept the body of knowledge developed by VIMS, the USGS and EPA on sediment – “good” or “bad”.

      and I’d do that especially so over the amateur armchair types..we hear from these days…

      sediment is a natural process that existed long before we can here and built stuff.

      rivers and streams “cut banks” – in the course of storm events…but the size and scope of runoff from impervious surfaces is far more than forest – or even pasture.

      Add to it stuff like antifreeze, oil, pet feces, and it’s not your grandfathers sediment much less something you’d want to try to bulk up wetlands with.

      wetlands do “grow” from – periodic flooding that then resides and gives the wetland a chance to recover.. and grow… if the inundation of the wetland is more than periodic – it can die and it becomes a contest of how far upland a wetland can grow – as fast or faster than the inundated land is submerged.

      it’s an ongoing study as we speak and TBD… so far…

      but I do expect the anti-Chesapeake Bay folks to begin using the sediment builds wetlands argument – regardless of what the science says – in fact – they’ll claim the science is wrong – and a conspiracy between the EPA, USGS and and VIMS – exists and they are hiding the fact that storm water regs are actually harming the bay -depriving it of the sediment it needs to build more wetlands..

      mark my words…..

  8. Here is an educational video from the Jim Bacon / TMT Wetlands Preservation Trust …

    https://youtu.be/YO7WhFapzXU

    As an aside, this is the same creek which Ken Cuccinelli sued the EPA claiming that there was no pollution coming from the wastewater.

    Jim – ecosystems tend to be pretty delicately balanced. Stormwater runoff is unlikely to create marshes. In a similar vein, nutrients in water ways cause plants to grow which lead to more wildlife. However, too much nutrient runoff causes algae blooms which suck up all the oxygen and kill everything.

    Something tells me the atrocious stormwater engineering in places like Accotink Creek cause problems rather than solving them.

    If you airdrop a thirsty man into the middle of Lake Michigan you may solve his thirst problem. However, he will likely drown.

    • I think this illustrates the gap between those who think they understand science and science itself.

      it may seem intuitive to some that if marshlands benefit from sediment that more sediment in rivers is a good thing.. but it doesn’t work that way and scientists can tell you why but in today’s time – everyone who can read – assumes they can be equal to a scientists by reading online and using logic and no where is this problem more apparent in the studies and believers that correlation is causation…

      If you believe what Jim implied – and I quote directly again: ” If Virginians are going to think seriously about resilience in the face of recurrent flooding and inundation, we need to better understand the fundamentals of how wetlands adapt to rising sea levels. On the one hand, higher levels of sediment from eroding rivers and streams creates a problem for Chesapeake Bay ecosystems, and is considered to be bad thing. Strict and expensive storm-water management regulations going into effect in Virginia is aimed at cleaning up the Bay. But, ironically, sediment in the right places — in threatened marshlands — can help Bay ecosystems adapt to rising sea levels. Is it possible that there is “good” sediment and “bad” sediment? We may need to adopt a more nuanced approach toward sediment. McGlathery’s work will prove invaluable.”

      it calls into question the entire idea of stormwater management… and I’m quite sure that – that’s NOT what McGlathery was saying.. but it sorta got picked out of the context.

      the nature of tidal flooding is not understood here apparently.. flood tides can build up wetlands but it the flooding goes higher that the wetland – it will also invade the land behind the wetlands… it’s the nature of sea level…

      think of it like building a flood wall in Richmond or a levee on the Mississippi – yes – you can keep the flood out where the wall/levee is but you can’t have a levee/wall along the entire coastline or river edge… and where-ever there is no wall/levee or higher-level wetland – the water invades…

      now – take a look at ANY small part of the Chesapeake Bay shoreline and you can see that there is no way to keep storm surges out unless you wall off the entire shoreline – otherwise the water just goes around somewhere else.

      look at the Mississippi when it is in flood and what do people do? they build levees around their homes… because that’s more feasible that trying to build levees for miles of shoreline..

      the whole idea of thinking more sediment will prevent sea level flooding on the coastlines is just wrong-headed.. it betrays a fundamental misunderstanding of how sea level flooding works..

      all you’d get from doing away with storm water programs will be a suffocated and dead bay …but sea level flooding would not be stopped – … along any area where there is not a wall.

      \

      • “The whole idea of thinking more sediment will prevent sea level flooding on the coastlines is just wrong-headed.”

        Who ever suggested this? Larry, your ability to misinterpret and misrepresent what I write is simply breathtaking.

        Here’s the operative language: “Sediment in the right places — in threatened marshlands — can help Bay ecosystems adapt to rising sea levels.”

        Sediment that gets dumped into the James River and sluices into the Chesapeake Bay is NOT “in the right places.” It creates ecological havoc. I have written extensively on the subject. I NEVER suggested that the desirability of sedimentation in wetlands is an excuse for eliminating stormwater regulations. Never. Where do you get off suggesting I have? Such grotesque distortion of what I have written is highly irresponsible.

        Instead of assuming that I hold some ridiculous, indefensible position, why don’t you ask for clarification?

        • Jim – I donj’t think I misrepresent when I’m quoting your exact words as I will again:

          ” If the replenishment of sediment is blocked, the marshes could die as water levels rise”

          ” On the one hand, higher levels of sediment from eroding rivers and streams creates a problem for Chesapeake Bay ecosystems, and is considered to be bad thing. Strict and expensive storm-water management regulations going into effect in Virginia is aimed at cleaning up the Bay. But, ironically, sediment in the right places — in threatened marshlands — can help Bay ecosystems adapt to rising sea levels. Is it possible that there is “good” sediment and “bad” sediment? We may need to adopt a more nuanced approach toward sediment. McGlathery’s work will prove invaluable.”

          Now Jim – what sediment to you think is getting “blocked” and how?

          I think you misrepresent YOURSELF when you use words this way – then claim they don’t mean what they imply.

          and I have asked you to be more clear and specific – not just on this – but especially so here as to what you mean because there is no way to have “good” or “bad” sediment as a choice… either you use storm management to reduce it or you do not.

          what would you suggest otherwise?

          I don’t misrepresent you – I take you at your word – but sometimes your word is not clear and specific but instead like it is here – using inference.

          answer one question here please –

          how would you get more sediment to downstream wetlands without putting more sediment and other runoff contaminates into the rivers upstream and inevitably that increased sediment further damages the estuary?

        • re: ” Instead of assuming that I hold some ridiculous, indefensible position, why don’t you ask for clarification?”

          actually I have several times as I have asked what you meant by your inferences…

          please clarify.

  9. Here’s another educational video from the Jim Bacon / TMT Wetlands Preservation Trust … this one documenting the fine effort being put forth by the people of Richmond in using stormwater runoff as a wetlands preservation tool.

    https://youtu.be/nujemyc6ZU4

    Thank goodness you guys don’t pay your fair taxes and fix this mess.

  10. Don, Here’s a whole bunch of videos about wife beating: http://www.bing.com/videos/search?q=wife+beating&qpvt=wife+beating&FORM=VDRE
    Yeah, it’s a real problem. You can’t just wish it away.

    That’s the same logic you apply to me. Your implication is that I am somehow unappreciative of storm water management issues and the need for upgrading our stormwater infrastructure. Incomprehensibly, you seem to think I’m against doing anything about the problem in Henrico County.

    Here’s a selection of the most recent articles I’ve written on the subject:

    Suburbia’s Silent Stormwater Crisis: http://www.baconsrebellion.com/2014/06/suburbias-silent-storm-water-crisis.html

    Putting the Garden in Rain Garden: http://www.baconsrebellion.com/2014/05/putting-the-garden-in-rain-garden.html

    Reinventing the Formal Garden: http://www.baconsrebellion.com/2014/03/reinventing-the-formal-garden.html

    Stressed Out Stormwater: http://www.baconsrebellion.com/2013/09/stressed-out-storm-water.html

    Let me quote from that last story: “As Bacon’s Rebellion readers know, I strenuously oppose most taxes. But I’m open to the idea of a storm-water utility fee in my home jurisdiction of Henrico County, and I think it ought to be structured like Richmond’s. ”

    Repairing Waterways One Subdivision at a Time: http://www.baconsrebellion.com/2013/03/repairing-waterways-one-subdivision-at-a-time.html

    You and Larry have commented on some or all of these articles, so it’s not as if you didn’t read them at some point. I’m used to Larry routinely misrepresent/misinterpret what I write, but I expect better of you, Don!

  11. What is it about the question, “Is it possible that there is ‘good’ sediment and ‘bad’ sediment?” that you don’t understand?

    Do you understand the difference between a question and a declarative statement?

    Do you understand the difference between wondering about something and making a dogmatic pronouncement?

    Can you grasp the obvious fact here that I’m acknowledging that there is such a thing as “bad” sediment — as I have written about repeatedly on this blog?

    • I understand that your “meaning” is not clear and explicit and before you talk about “good” or “bad” – you need to explain how that would work in a river and estuary …as you do not have a choice of one or the other.

      Jim – I think you are playing with words here… not being clear.. and not clarifying.. and that’s what I’m calling the BS on…

      how do you get “good” sediment without having “bad sediment” also?

    • So, Jim … what was your point? If there were no human beings on Earth there would still be sediment washed into marshland ecosystems and that would be good? Or, that some wastewater borne sediment caused by human development is good?

      • Yes, my point is that maybe some wastewater sediment could be beneficial in the right volume and in the right places. I’m not say that *is* the case, I’m just wondering if it might be. Who knows, maybe too much sediment will suffocate wetlands in muck. I don’t know. What I am saying is that I’ve never before heard (until Carol Bova mentioned it) that sediment might help wetlands adapt to rising sea levels. And that maybe it’s something worth examining scientifically.

        Larry G, of course knows all, and has concluded that not only is there absolutely no truth to the speculation but that the question is so beyond the pale that there is no point in even looking into it…. even though Ms. McGlathery explicitly says that wetlands depend upon sedimentation to keep up with rising flood waters.

  12. there must be something about how we think about these things. I see it in other issues where a problem is identified and a potential solution alluded to but it’s totally out in left field – it’s “ideas” that pretend they are feasible when they are not. So I do cut to the chase.. if someone is going to muse about things like “good” or “bad” sediment – I want to at least see some sort of a possible practical approach. Otherwise – we’re just blathering idiocy… all due respect.

    • Dear LarryG: Not blathering idiocy, no. You say, “how do you get “good” sediment without having “bad sediment” also?” You have a wonderful sense of humor! I really loved your pun: “The biggest tributary for the CBAY is the Susquehanna which is heavily damned yet still dumps enormous loads of sediment . . ..” Damned right it’s damned; dammed too! In fact that’s the current fight over in MD Gov. Hogan’s office, whether to dredge some of the accumulated sediment behind the Conowingo Dam in order to allow more up-river sediment to be trapped there, as opposed to leaving the dammed basin full which means additional sediment goes over the dam — which is no worse than the sediment flow which would have occurred if there were no dam, of course.

      Consider that you started this discussion with: “Perhaps I’m not understanding but sediment does not “climb” up on top the marshes.. it settles into the bottom and one way we know this is that we have to dredge ship channels to keep them clear and we have dead zones where sediment has settled and suffocated bottom life. Finally – think about tides and how they cover the marshes.. and at certain times – higher tides cover many more marshes and storm surge tides – destroy marshlands and wetlands – as we have seen when storms cut across the outer banks barrier islands. And where do marshes that exist on the barrier islands get “sediment” anyhow? The idea that sediment is an antidote to rising seas … is wrong-headed “science”.”

      I don’t agree at all that it’s “wrong-headed ‘science’.” Sand rarely ‘climbs’ up onto marshes, but mud does! You are confusing the rapid erosion and movement of silt along a swift-moving, gravel-sand-bottomed, white-water stream, and on down into the shipping channels of the Bay, with the normal, indeed essential, deposition of organic silt in our tidal marshes. Yes, there’s a critical balance between healthy and unhealthy quantities of tidal silt; silt also differs qualitatively, on a scale from sandy to suspended mud to organics. Bethel Beach and the Winter Harbor marshes in Mathews are in good shape with largely clear water in winter, and around the Blackwater River area where I live it’s the same, but the suspended organic matter in summer builds up around here forming “pluff mud” on the bottom. It contains the food for our oysters and at the same time can come down fast enough to smother the reeds and the oysters trying to make a comeback in their old Mobjack Bay habitat. It’s “natural” silt but with all the fertilizer and the faster surface runoff there’s nothing natural about the volume. Yet my oysters are surviving, and increasing in number.

      This kind of silt is fine enough to flow with the tide to the head of every waterway twice daily, and to wash even further inland with every major storm. This silty mud will eventually compact into marsh peat, and later new soil. Maybe it will accumulate fast enough and the marsh grasses will grow fast enough to counteract the sinking coastline and rising ocean; maybe not. If not, the open waters in our coastal estuaries will widen and the coastline will retreat, again, as it has many times in the geologic past [the Park Rangers at Kenilworth Gardens on the Anacostia River in DC love to show you their collection of sharks teeth collected from the sandy soil around there, dating from when the oceans last rose so radically that waves broke in the surf along the Fall Line]. The only thing different this time? Man lives here now, and we’ll try to hold the sea back, rather than “go with the flow” and abandon all those coastal vacation homes that had no business being built there anyway.

      The science of climate change is something that interests readers of this blog and I hope we continue to talk about it. The fact is, at the end of the Jurassic about 65 million years ago, and again in the middle of the Eocene about 35 million years ago, there were fairly rapid warm-ups of the climate, on the order of tens of degrees, causing sea level increases of hundreds of feet that lasted for millions of years. We now know that both warm-ups, and contemporaneous kill-offs of huge numbers of species, were associated with (triggered by?) meteors striking the earth (one in the Yucatan, and one in the southern Chesapeake). Some similar, earlier kill-offs/warm-ups were associated with massive volcanic activity in what is now our Northwest, and in Siberia. Compared to those, the effects of our global carbon-dioxide blanket are trivial, although very real. The point is, in those cases the coastline moved inland very rapidly, far too fast for the marshes to keep up until things stabilized at new heights. Maybe our more gradual impact this time around will allow some accommodation of sea level rise to occur naturally. I think that’s Jim’s point.

  13. “just blathering idiocy…”
    Indeed, and not from Bacon.

  14. Getting old and boring…
    larryg needs a new bone:
    The Marxist roots of the global warming scare
    http://www.renewamerica.com/columns/vernon/080616

    Jun 16, 2008 – By Wes Vernon The late Natalie Grant Wraga once wrote, “Protection of the environment has become the principal tool for attack against the …

    • All dams catch sediment. Each dam built ends up with a predicted lifespan when what it can hold gets smaller and smaller as it fills up more and more with sediment.

      But it’s a mistake to think a dam holds back all sediment – it does not.

      water goes over a dam – muddy water heavy with sediment goes over the dam in such volumes that the dam cannot contain it…

      storm ponds are rated according to how much they can hold – they usually are rated for 2yr or 10yr storm events which basically says how much they can hold before the water – laden with silt goes over them and into the creeks and rivers.

      sediment in rivers that overruns the banks – does deposit silt – the James river has millions of acres of rich farmland that was laid down over eons of flooding…

      and as Acbar stated – with verbosity that rivals mine.. we had in the past very large rivers and inland oceans and billions of sharks who left their teeth behind so that today in most river banks you can find sharks teeth – it makes a fine outing in a canoe ..to find them..

      so rivers do transport and deposit silt through periodic flooding..

      but at sea level in the estuaries – even with major river floods – they have almost no effect on the level of the water – muddy or not… but tidal does but by the time the water gets to tidal – it has dropped most of it’s sediment – as the muddy waters hit slack waters.. but even the mud left cannot “climb” the wetlands – it gets there at high tide when the high tide recedes.

      wetlands, however, do not build impenetrable flood walls that keep out ever increasing high tides.. the water just goes right past them to flood the land behind them.

      What Vims and the USGS and others have said is that there are several factors in place – subsistence and increasing sea levels – especially at surge tides but beyond that – the more man-built flood walls their are – the more it will funnel even more water to where the wetlands are.. like levees on the Mississippi while protecting some areas – actually make flooding worse on others.

      at this point – it doesn’t really matter about silt deposition because these other factors are much larger..

      it’s just a misunderstanding about how tides work.. you cannot stop flood tides and if they occur more frequently at higher levels then they have the real possibility of not building wetlands but drowning them.

      I do not pretend to know how all of this works – but I do have confidence that science does and I’ll believe what they have to say about it – at least before I listen to a bunch of armchair types who don’t know – that they don’t know.

      but the thing I reacted to was when Jim was speculating that holding back silt might be holding back “good” silt – that could build wetlands.

      and all I can say – is .. to this point – I’ve not seen a whole lot of science on that issue and yes I’m pretty skeptical about laypeople positing what science is still working on. If someone has some credible studies from real scientists – by all means throw them on table.

  15. larryg- you are so brilliant that you lost me along the way….let’s do this:
    The Marxist roots of the global warming scare
    http://www.renewamerica.com/columns/vernon/080616
    I want your analysis/opinion.

    • ElSidd – I’d have to defer to you to tell me what Renew America has to do with Sediment, Wetlands and Climate Change…

      Have they commented on the issue(s)?

  16. Why don’t you read the article. Then ask what it is that is not understandable to you.
    There are no “they” to comment..

  17. Well, Yes, Too “out there “. I notice that you do not tangle with ideological issues of the Big Time like Communism/Marxism/ Nazism. Maybe wisely…
    If you do not “get it” from reading the article, no hope for me to explain it to you.
    Go right on and explain everything about everything to everyone about everything that you do. God Bless you.

  18. Oh I can tangle with it – I just need the other person to weigh in with their views… at this point .. you’re asking about these ideologies without a real context.. that leaves a lot of territory unless you’re equating it to the Agenda 21 issue…

  19. “a lot of territory” is usually covered by a few “USEFUL IDIOTS”.
    I don’t think this is a worthwhile discussion because you seem to be a prime UI.
    What are you equating to Agenda 21?

  20. No, larryg, since you are the smartest, brightest in the room/blog, wherever,— explain all: including Earth Charter, Gorbachev, Maurice Strong, Al Gore.
    I will definitely respond in corrections as to what I KNOW.
    Go right ahead. What do you know? About what? JEEEZE LOUIZZE, hard question since you know everything about everything.

    • Jeeze Louise!

      😉

      I’m pretty ignorant actually.. we all are -just on different subjects.. and I certainly claim my share and more but I do have opinions… and I don’t hide what I think.. pretty straight forward about it… and you?

  21. Said “with verbosity that rivals mine” — Hah! Impossible – but I’ll accept the compliment!

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