Comments on: Coastal sediment needs – let’s get real, folks! http://lacoastpost.com/blog/?p=11886 Fri, 03 Sep 2010 21:11:19 +0000 hourly 1 http://wordpress.org/?v=3.0 By: Engstfeld http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4944 Engstfeld Mon, 02 Nov 2009 09:32:16 +0000 http://lacoastpost.com/blog/?p=11886#comment-4944 All the more reason NOT to recycle paper, perhaps? All the more reason NOT to recycle paper, perhaps?

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]]> By: Mike Waldon http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4633 Mike Waldon Wed, 16 Sep 2009 03:05:14 +0000 http://lacoastpost.com/blog/?p=11886#comment-4633 I've always been troubled by one aspect of these calculations. I'm unclear on just how much of the delta is made from solids carried by the River. Plant mass comes primarily from the atmosphere and dissolved minerals in water. Shell material originates as dissolved material from the River or from saltwater. Certainly deltas form at the mouthes of rivers, but at least a part of this mass is originating as dissolved minerals and atmospheric carbon that is fixed into solid form by the high productivity at the estuarine interface. This is analogous to the question "Where do trees come from?" The answer may surprise some until you think about it. I've read that most of the mass of a tree comes out of the air through fixation of carbon. If it did not, you would see big depressions next to big trees. Thanks for the opportunity to comment and probably demonstrate my ignorance. --Mike I’ve always been troubled by one aspect of these calculations. I’m unclear on just how much of the delta is made from solids carried by the River. Plant mass comes primarily from the atmosphere and dissolved minerals in water. Shell material originates as dissolved material from the River or from saltwater. Certainly deltas form at the mouthes of rivers, but at least a part of this mass is originating as dissolved minerals and atmospheric carbon that is fixed into solid form by the high productivity at the estuarine interface.

This is analogous to the question “Where do trees come from?” The answer may surprise some until you think about it. I’ve read that most of the mass of a tree comes out of the air through fixation of carbon. If it did not, you would see big depressions next to big trees.

Thanks for the opportunity to comment and probably demonstrate my ignorance. –Mike

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]]> By: Writing a coastal proscription, an “unplan” | LaCoastPost http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4567 Writing a coastal proscription, an “unplan” | LaCoastPost Mon, 07 Sep 2009 15:52:47 +0000 http://lacoastpost.com/blog/?p=11886#comment-4567 [...] Coastal sediment needs – let’s get real, folks! [...] [...] Coastal sediment needs – let’s get real, folks! [...]

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]]> By: Admin http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4426 Admin Thu, 03 Sep 2009 12:40:04 +0000 http://lacoastpost.com/blog/?p=11886#comment-4426 Thanks for your comment Jennifer. It's great to see input from folks with recent new data collected in the field! Thanks for your comment Jennifer. It’s great to see input from folks with recent new data collected in the field!

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]]> By: Jennifer Roberts http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4304 Jennifer Roberts Wed, 26 Aug 2009 17:24:19 +0000 http://lacoastpost.com/blog/?p=11886#comment-4304 I just completed a (MS) research project tracking the response of marsh vegetation to hurricane sedimentation. I can tell you that Hurricane Ike pushed in more sediment onto a marsh in Cocodrie than Hurricane Gustav. Ike was a bigger storm and it moved west of the marsh. Beyond knowing where the sediment was coming from when addressing storm sedimentation and sedimentation in general we need to remember that it is the volume of both the sediment and organic matter that sustains our marshes. I saw an increase in soil organic matter (root) volume post-sedimentation. It is a combination of sediment and organic matter that sustains our marshes. I've been convinced that it is the volume of dirt and plant material not the mass of the stuff that we need to look at. I just completed a (MS) research project tracking the response of marsh vegetation to hurricane sedimentation. I can tell you that Hurricane Ike pushed in more sediment onto a marsh in Cocodrie than Hurricane Gustav. Ike was a bigger storm and it moved west of the marsh.

Beyond knowing where the sediment was coming from when addressing storm sedimentation and sedimentation in general we need to remember that it is the volume of both the sediment and organic matter that sustains our marshes. I saw an increase in soil organic matter (root) volume post-sedimentation. It is a combination of sediment and organic matter that sustains our marshes. I’ve been convinced that it is the volume of dirt and plant material not the mass of the stuff that we need to look at.

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]]> By: Mark Ford http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4302 Mark Ford Wed, 26 Aug 2009 16:21:31 +0000 http://lacoastpost.com/blog/?p=11886#comment-4302 Len, I think the jury is still out on this issue of storms. There is a body of data out there indicating substantial accretion from storms of various strengths. Gene Turner documented a lot of sediment accretion after Katrina and Rita. At the Pearl River, there was strong evidence of erosion, but also accretion, and until we measured soil elevation changes, which were positive by several centimeters, we were not sure if that ratio was negative or positive. From other storms (such as Ivan), people have documented postive elevation gains from sedimentation. Ivan is just one of numerous additional examples. There are techniques to determine the source of the sediments, whether from the bays, the Gulf, or internally from the marshes them selves. We need to futher investigate. And yes, in some cases, the storms do just move sediments around. I would assume that may be due to where in the storm a particular site may be. You'll get very different impacts if you are in the forward left quadrant of a storm, versus the much stronger right forward quadrant. Len,

I think the jury is still out on this issue of storms. There is a body of data out there indicating substantial accretion from storms of various strengths. Gene Turner documented a lot of sediment accretion after Katrina and Rita. At the Pearl River, there was strong evidence of erosion, but also accretion, and until we measured soil elevation changes, which were positive by several centimeters, we were not sure if that ratio was negative or positive. From other storms (such as Ivan), people have documented postive elevation gains from sedimentation. Ivan is just one of numerous additional examples.

There are techniques to determine the source of the sediments, whether from the bays, the Gulf, or internally from the marshes them selves. We need to futher investigate.

And yes, in some cases, the storms do just move sediments around. I would assume that may be due to where in the storm a particular site may be. You’ll get very different impacts if you are in the forward left quadrant of a storm, versus the much stronger right forward quadrant.

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]]> By: Admin http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4292 Admin Tue, 25 Aug 2009 12:02:04 +0000 http://lacoastpost.com/blog/?p=11886#comment-4292 Oliver- I had the same thought when I saw Harry's presentation to the CPRA. On the other hand, based on conversations with delta experts my sense is that there is a strong geological consensus that the storm accretion:erosion ratio is negative, not positive. Remember, the ultimate source of all deltaic sediment was/is the river. Storms just move it around and generally take away more than they put back where it's needed. Oliver-
I had the same thought when I saw Harry’s presentation to the CPRA. On the other hand, based on conversations with delta experts my sense is that there is a strong geological consensus that the storm accretion:erosion ratio is negative, not positive. Remember, the ultimate source of all deltaic sediment was/is the river. Storms just move it around and generally take away more than they put back where it’s needed.

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]]> By: Admin http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4291 Admin Tue, 25 Aug 2009 11:49:06 +0000 http://lacoastpost.com/blog/?p=11886#comment-4291 David- Your comment is well taken. I just saw a map of the corps' proposed borrow sites for the levee clay. As you said, the resulting holes are all within the very delta that we're trying to save by borrowing from Peter to pay Paul. David-
Your comment is well taken. I just saw a map of the corps’ proposed borrow sites for the levee clay. As you said, the resulting holes are all within the very delta that we’re trying to save by borrowing from Peter to pay Paul.

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]]> By: Oliver Houck http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4288 Oliver Houck Mon, 24 Aug 2009 20:31:57 +0000 http://lacoastpost.com/blog/?p=11886#comment-4288 Re sediment budget, has anyone calculated the amount of seds pushed inland by coastal storms? I remember seeing the buildup in St Bernard wetlands post Katrina at several inches. Not saying coastal storms are good, just that I've not seen gross estimates of this source of supply and its fate if the big linear levees go in. Even with levee gates, storm time would seem to be when the gates shut down. Re sediment budget, has anyone calculated the amount of seds pushed inland by coastal storms? I remember seeing the buildup in St Bernard wetlands post Katrina at several inches. Not saying coastal storms are good, just that I’ve not seen gross estimates of this source of supply and its fate if the big linear levees go in. Even with levee gates, storm time would seem to be when the gates shut down.

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]]> By: David Muth http://lacoastpost.com/blog/?p=11886&cpage=1#comment-4285 David Muth Mon, 24 Aug 2009 17:42:31 +0000 http://lacoastpost.com/blog/?p=11886#comment-4285 Len: Don't forget, most of the six SDEs for New Orleans 1 in 100 year protection will come from the delta, so in a sense you have to add that onto the deficit that Roberts projects. Thousands of acres of bottomland hardwood forest, a deltaic ecosystem that is actually on a steeper decline than delta marshes, will be destroyed, since the clay needed for levees underlays bottomland hardwoods for the most part. in other words, in order to save the delta, we have to destroy the delta. Morganza, Donaldsonville, the newly federalized Plaquemines levees, plus future lifts for enhanced LACPR protection will increase the deficit. Len:

Don’t forget, most of the six SDEs for New Orleans 1 in 100 year protection will come from the delta, so in a sense you have to add that onto the deficit that Roberts projects. Thousands of acres of bottomland hardwood forest, a deltaic ecosystem that is actually on a steeper decline than delta marshes, will be destroyed, since the clay needed for levees underlays bottomland hardwoods for the most part. in other words, in order to save the delta, we have to destroy the delta. Morganza, Donaldsonville, the newly federalized Plaquemines levees, plus future lifts for enhanced LACPR protection will increase the deficit.

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