1 MODELING OF LAND BUILDING IN THE MISSISSIPPI DELTA: A TEMPLATE FOR RECONSTRUCTION Wonsuck Kim & Gary Parker, University of Illinois As part of a much larger team led by C. Paola (NCED) and R. Twilley (CLEAR)

2 THE ORIGINS OF OUR LAND-BUILDING TECHNOLOGY: CAN HUMANS JUMP-START THE NATURAL DELTA- BUILDING PROCESSES OF RIVERS?

3 THE NATURAL PROCESS OF DELTA LOBE CONSTRUCTION AND SWITCHING Lobe gif from M. Wolinsky

4 DELTA MADE BY HUMANS: TAILINGS BASIN OF AN IRON MINE, LABRADOR, CANADA Sediment disposal rate: ~ 24 Mt/yr ~ 2.4 km

5 DELTA MADE BY HUMANS: TAILINGS BASIN OF AN IRON MINE, MINNESOTA Sediment disposal rate: 21 Mt/yr ~ 3 km

6 WE HAVE DEVELOPED AND VERIFIED NUMERICAL MODELS THAT DESCRIBE THE OVERALL EVOLUTION OF THESE DELTAS DECADES INTO THE FUTURE

7 HOW MUCH SEDIMENT IS CURRENTLY AVAILABLE FOR DELTA BUILDING IN THE MISSISSIPPI DELTA? Input: ~ 208 Mt/yr Wax Lake Delta: ~ 34 Mt/yr Atchafalaya River: ~ 84 Mt/yr Lower Mississippi River: ~ 124 Mt/yr Atchafalaya Delta: ~ 50 Mt/yr Suspended sediment loads

8 Atchafalaya River Mississippi River Wax Lake Delta The delta started to formed in 1973, when it received increased flow from the Atchafalaya River. Its growth has been monitored ever since. TEST OF CONCEPT: NUMERICAL MODEL OF EVOLUTION OF THE WAX LAKE DELTA

9 OUR MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST Before start of delta growth

10 THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST Yellow: 38 Mt/yr White: 25 Mt/yr (suspended load)

11 THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST Yellow: 38 Mt/yr White: 25 Mt/yr (suspended load)

12 THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST Yellow: 38 Mt/yr White: 25 Mt/yr (suspended load)

13 THE MODEL CAN REPRODUCE THE WAX LAKE DELTA’S PAST Yellow: 38 Mt/yr White: 25 Mt/yr (suspended load)

14 PREDICTIONS INTO THE FUTURE OF THE WAX LAKE DELTA HIGH: Solid line, 38 Mt/yr; LOW dotted line: 25 Mt/yr (suspended load) LOW HIGH LOW

15 MIGRATION OF THE MODEL FROM WAX LAKE TO THE MISSISSIPPI RIVER BELOW NEW ORLEANS: Two diversions: Barataria Bay and Breton Sound (CLEAR plan)

16 POTENTIAL SEDIMENT FOR DELTA BUILDING: 45% OF 124 Mt/yr, OR 56 Mt/yr (~ 3 iron mines) Barataria Bay: 28 Mt/yr delivered 11 Mt/yr captured Breton Sound: 28 Mt/yr delivered 11 Mt/yr captured 45% of floodwater and sediment diverted.

17 SCENARIOS MODELED 100 year simulations from 2010 Base case: Subsidence: 5 mm/yr; sea level rise: 2 mm/yr Variant parameters Subsidence: 1 mm/yr, 10 mm/yr Sea level rise: 0 mm/yr, 4 mm/yr Image from M. Wolinsky

18 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE Takes only about 0.1 years to build these initial deltas

19 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

20 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

21 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

22 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

23 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

24 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

25 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

26 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

27 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE

28 PRELIMINARY RESULTS FOR LAND-BUILDING: BASE CASE Base case: 918 km 2 of new land

29 VARIATION: SEA-LEVEL RISE RATE = 0 mm/yr, SUBSIDENCE = 5 mm/yr Solid line: variant case Dotted line: base case 1002 km 2 of new land

30 VARIATION: SEA-LEVEL RISE RATE = 4 mm/yr, SUBSIDENCE = 5 mm/yr Solid line: variant case Dotted line: base case 845 km 2 of new land

31 VARIATION: SEA-LEVEL RISE = 0 mm/yr, SUBSIDENCE = 1 mm/yr Solid line: variant case Dotted line: base case 1217 km 2 of new land

32 VARIATION: SEA LEVEL RISE = 2 mm/yr, SUBSIDENCE = 1 mm/yr Solid line: variant case Dotted line: base case 1101 km 2 of new land

33 VARIATION: SEA LEVEL RISE = 2 mm/yr, SUBSIDENCE = 10 mm/yr Solid line: variant case Dotted line: base case 753 km 2 of new land

34 VARIATION: SEA-LEVEL RISE = 4 mm/yr, SUBSIDENCE = 10 mm/yr Solid line: variant case Dotted line: base case “Worst case”: still 701 km 2 of new land And extra land-building due to organics is not yet included

35 IN ORDER FOR THE DIVERSIONS TO BE SUCCESSFUL, CONTROL STRUCTURES AND SHORT GUIDE CHANNELS, NOT OVERFLOW POINTS, ARE NEEDED We need to get as much sand as possible into the new deltas. The present Caernarvon diversion, while helpful, delivers mostly mud. We know how to build the control structures that divert sand as well as mud, because we built the Old River Control Structure to regulate flow into the Atchafalaya River.

36 SLURRY PIPELINES CAN BE HELPFUL TO START LAND- BUILDING IF SUSTAINED FOR MORE THAN A FEW YEARS, HOWEVER, THEY CAN BUILD DELTA SLOPES THAT ARE TOO STEEP. ebuilder&nid=31&pid=20&pnid=24&tmp=home

37 NEXT STEP: BUILD IN THE FINE STRUCTURE Our field effort on the Wax Lake Delta is our main template. (m) The land-building model predicts overall topography. We are using field measurements to build in the statistical structure of bars/channels/edge effects/ etc. necessary for ecosystem modeling. Many species of fish like this edge zone near bars.

38 BUILD IN THE ECOLOGICAL COMPONENTS OF THE NEW DELTA Most of these components are already in place at Louisiana State University and within the CLEAR group in Louisiana. NEXT STEP:

39 NEXT STEPS: CONSIDERATIONS OF SUCH FACTORS AS Effect of diversions on Mississippi River upstream Coastal sediment supply Storm surge Navigation Socioeconomic implications: e.g. oyster farms, shrimp POLITICAL WILL AMBITIOUS PROJECTS ARE POSSIBLE! Parker’s great-grandfather and great uncle were construction workers on this first bridge to span the Mississippi River in New Orleans Levee strengthening will be needed in the short term

40 Most of the Mississippi Delta, some 10,000 square miles, lies less than three feet above sea level. Beset by land subsidence and rising sea levels, much of this vast area will inexorably sink beneath the waters by the end of this century. BRUCE BABBITT

41 Most of the Mississippi Delta, some 10,000 square miles, lies less than three feet above sea level. Beset by land subsidence and rising sea levels, much of this vast area will inexorably sink beneath the waters by the end of this century. BRUCE BABBITT Before major human intervention, the Mississippi Delta historically maintained itself with river slopes on the order of 3 ft of drop per 30 miles without sinking beneath the waters! How? The surface is NOT a static “board” that will sink because of its low slope – it is a DYNAMIC, self-maintaining surface that keeps itself from drowning by adding sediment to balance subsidence. Think about your bank account. If you withdraw $1,000 a month every month, you will go broke before long. How can you fix the problem? OUR REPLY

42 Most of the Mississippi Delta, some 10,000 square miles, lies less than three feet above sea level. Beset by land subsidence and rising sea levels, much of this vast area will inexorably sink beneath the waters by the end of this century. BRUCE BABBITT START DEPOSITING $1000 A MONTH! OUR REPLY

43 WE THINK THAT THE SCIENCE AND TECHNOLOGY EXISTS TODAY TO REBUILD A NEW, LIVING MISSISSIPPI DELTA Wax Lake gif from M. Wolinsky