From 2004-07 (while at URS Corporation) Bob Jacobsen was the technical manager, principal investigator, and report author for several important Southeast Louisiana coastal hydrology projects, including:
Maurepas Diversion Hydraulic Feasibility Study for the Louisiana Department of Natural Resources (now CPRA) and the USEPA.
The study targetted the key question posed by the USEPA: "will the water go where we want it to go." This question reflected four key physical objectives for a 2,000 cfs diversion of Mississippi River water into the 50,000 acre Maurepas Swamp:
1. Broad, uniform flow distribution and delivery of nutrients and fine colloidal sediment throughout the Swamp.
2. Reasonable retention times within the Swamp to achieve denitrification and avoid eutrophication impacts in the Blind River and Lake Maurepas.
3. Minimal impounding tailwater impacts to the gravity stormwater systems of nearby Garyville and Reserve, which drain to the Swamp.
4. Controlled velocities at sensitive diversion channel locations to prevent scour and erosion—e.g., the Interstate 10 bridge at Hope Canal.
Investigations featured extensive topographic and bathymetric surveying, a detailed project area Digital Elevation Model, collection and processing of hydrologic data to special precision requirements (associated with extremey low gradients), and modeling of fine-scale short-circuiting paths and 2D circulation within the Swamp, as well as modeling of community drainage system.
The project required the first-ever development and application of HPC/High Resolution 2D modeling to the analysis of wetland circulation and retention time. Bob Jacobsen initiated and planned the use of the ADvanced CIRCulation (ADCIRC) hydrodynamic code for the project, which was then being evaluated by the USACE and professional colleagues at LSU for storm surge modeling. Bob coordinated extensive support for the unique application from code authors Joannes Westerink and Rick Luettich thoughout the modeling effort, as well as organized the subcontract HPC services of WorldWinds, Inc. based in Slidell LA. First phase 2D mesh development and model testing were performed by Himangshu Das and directed by Chris Reed, with the URS coastal modeling center in Tallahasee FL. Bob Jacobsen planned and directed the second phase, which included:
a. Additional topographic and bathymetric refinements of the mesh to better reflect the project area DEM.
b. Model calibration/validation using three periods of Swamp stage and velocity data.
c. 48 diversion simulations evaluating Swamp circulation and outfall management under a variety scenarios—alternate diversion rates, Lake Maurepas stages, and drainage inflows.
The simulations entailed a wide range of trouble-shooting efforts to overcome special problems in applying the ADCIRC code of the time to the diversion. Phase 2 simulations were implemented by Nathan Dill and Ben Jelley (WorldWinds, Inc.). As part of these efforts Jacobsen and Dill completed a first-ever coupling of ADCIRC with a 1D drainage model (for Garyville and Reserve developed by the URS Metairie LA office). Nathan Dill also parallelized the Lagrangian random-walk particle algorithm to run on the HPC to assist in evaluating short-circuiting and retention time.
This project was part of the Louisiana Coastal Protection and Restoration Study and featured a detailed harmonic analysis of tidal constituents in the Pontchartrain Basin (including over 110 time series from 40 gages), together with an evaluation of the capability of the HPC/High Resolution ADCIRC model to replicate regional tidal propagation in the large, complex estuary. The study also analyzed the model’s capability to assess the impact of closure structures at the Rigolets and Chef Menteur Passes on tidal prism. ADCIRC simulations were implemented with support from Nathan Dill and Ben Jelley (WorldWinds, Inc.).
Interaction of Hurricanes and Coastal Landscape Features: A Literature Review (with Joseph N. Suhayda, PhD—principal author); prepared in 2006 for the USACE-NOD as part of the Louisiana Coastal Protection and Restoration Study. The Report addressed a variety of coastal features—including barrier islands, forested swamps, and marshes—and hurricane storm characteristics. The interactions encompassed impacts of hurricanes on the coastal landscape features and of the coastal landscape features on hurricanes. The latter included impacts both to storms characteristics (hurricane structure, intensity, and local wind stress) and storm surge—surge elevation, currents, and waves.