Presentation on theme: "Three options follow. They are all valid and each has pros and cons. The goal of each is to get “a” path through the subbasin and to the coastline bounding."— Presentation transcript:
Three options follow. They are all valid and each has pros and cons. The goal of each is to get “a” path through the subbasin and to the coastline bounding the sea/ocean (Gulf of Mexico). This will satisfy the need to navigate a coastline and would provide a generalized path for stuff to get through the subbasin that could be expanded as flow direction information becomes available. Option 1 matches the NOAA CAF estuary mixing zone delineation and uses the HUC10 delineation between and 04. Artificial paths would be extended from Lac Des Allemands through Lake Salvador to the HUC 10 boundary. The coastline would extend all the way up to Lake Salvador. Option 2 extends the path through to the edge of Barataria Bay. The coastline would bound Barataria Bay, which is how the NHD currently is delineated. In this case, we would have 2 estuaries, one with artificial paths through the estuary and one with coastline around the estuary. Option 3 extends the path all the way to the Gulf of Mexico. The coastline would be delineated by connecting the barrier islands. This would be the easiest to maintain - a more stable “coastline” with fewer reach codes. Question: If we poured a bunch of red dye into Lac Des Allemands, would it eventually Make it to the Gulf of Mexico in a general path that matches the proposed path – i.e. does the water actually move in that direction through those waterbodies?
“Lac Des Allemands is fed by numerous bayous in the Barataria Basin surrounding the lake, including Grand Bayou and Bayou Chevreuil. The Basin is criss-crossed by bayous, access canals, drainage canals, and navigation channels, including the Intracoastal Waterway and the Barataria Waterway. Most of the Basin is at sea level. Lac Des Allemands is a shallow lake, with a maximum depth of 10 feet and an average depth of five feet. It measures about 5.5 miles long and 6.5 miles wide. Lake waters flow southeast into the Bayou Des Allemands, then on to Lake Salvador and eventually to the Gulf of Mexico. Bayou Des Allemands provides a public boat ramp for access to Lac Des Allemands and Lake Salvador.” “The community of Des Allemands, which lies along the banks of Bayou Des Allemands, suffered considerable storm surge flooding from Lac Des Allemands and Lake Salvador during Hurricane Ike in September of The Bayou currently has no flood control structures (pumps, weirs, etc.). The U.S. Army Corps of Engineers, the Louisiana Department of Transportation and Development, and the Lafourche Basin Levee District conducted a feasibility study pertaining to a 57-mile long hurricane levee through Bayous Des Allemands, connecting to the Davis Pond Diversion Project. Davis Pond diverts Mississippi River freshwater into the upper portion of the Barataria Basin, but does not connect directly to Lac Des Allemands.”
At maximum flow, Davis Pond would add three inches of water to Lake Cataouatche, one inch to Lake Salvador and none at all to Lake des Allemands. For the Mississippi River, diversion at the maximum rate would have removed only 14 cubic feet per thousand cubic feet from Monday’s flow of 759,000 cubic feet per second past the Davis Pond structure.
I would encode flow direction on the “named” bayous into Lac Des Allemands - and only the named bayous. Bayou Verret starts at the headwaters and flows into intervening bayous and then into Lac Des Allemands so we could have a flow path all the way up to the headwaters. Bayou des Allemands connects Lac Des Allemands to Lake Salvador so we can get to Lake Salvador. The Davis Pond Project described in previous slides is an “inter-subbasin connection” with the Mississippi River and that path should be encoded into Lake Catahoutche and then Lake Salvador. I think this flow path is pretty good. If we did option 1, we would stop here. For option 2: Bayou Perot and Bayou Rigolettes could connect Lake Salvador to Little Lake and then thorough Little Lake to Barataria Bay and stop. There was an oil spill in Bayou Perot and there might be good info about where the oil went, indicating flow direction perhaps. see ttp://www.noaawatch.gov/2007/bayou_perot_oilspill.php ttp://www.noaawatch.gov/2007/bayou_perot_oilspill.php It looks like perhaps a path on the east through The Pen that would flow into Little Lake as well. See For option 3: I would just draw a straight Artificial Path from Little Lake through Barataria Bay and hook it up with the coastline. Any attempt to make it look good would be dishonest.