...creating stormwater-storage systems in urban parks and even parking garages, as well as managing soil moisture to maintain hydration and reduce subsidence.
In river environments, the approach also includes creation of upstream, secondary and parallel side channels designed into rural and urban landscapes to create storage buffers and lots of new riverfront property for future development. It also includes renewed efforts to reach out to other stakeholders in the watershed and seek a holistic approach to dealing with water-management issues throughout the entire river system. Many deltas are greatly challenged by policy issues, as they are at the tail end of systems that often originate hundreds, even thousands of miles away and course through patchworks of sometimes antagonistic political entities.
But in the end, there will be a floodgate, a levee or a wall. At that point, engineers also are confronting the blue-sky- failure nightmare by trying to learn much more about the behavior of those mute flood-control structures under stress and, perhaps even more importantly, at rest between challenges.
Flood Control 2015, a 10-year initiative spawned by a Dutch consortium that now attracts international participation, is a multipronged effort to become smarter about reducing the risk of floods. It was inspired, in part, by the Dutch inspections of the devastation of Hurricane Katrina but also by their examination of the highly developed flood-fighting systems and facilities of the U.S. Army Corps of Engineers and California Dept. of Water Resources in Sacramento. The initiative seeks to develop a holistic, real-time data-driven approach to planning for and managing the inevitable disasters.
One of the beneficial outcomes of Katrina is that scientists all over the world realized they needed to look beyond their immediate geographic areas toward larger systems in order to effectively manage deltas, says Greg Smith, director of the U.S. Geological Survey National Wetlands Research Center in Lafayette, La. He says the idea is to view “river management and activities from the headwaters to the del- ta” as one system that ultimately affects how the landscape changes on the coast. “I think everyone, especially in this part of the country, has a new appreciation for that,” says Smith. “What people have not looked at is how other deltas in other parts of the world have been managed and what kind of results those efforts have produced.”
“The Mississippi Delta is not a sustainable system,” adds Smith. “It didn’t require a lot of in-depth science to figure that out after Katrina.” Between hurricanes Katrina and Rita in fall 2005, Louisiana lost more than 200 square miles of coastland, he says.
In an effort to “develop a community of practice and to share models and data,” NWRC formed the Delta Research and Global Observation Network (DRAGON) in fall 2007. The network’s goal is to develop a scientific framework for comparing, integrating and predicting the effects of key drivers and management practices in massive deltaic coastal systems, Smith says. “What we are looking at is the whole series of deltas around the planet and what kind of information is available that can offer insight into the future of the Mississippi River delta,” says Smith. But so far, he has found that very few comparative studies exist.
Other deltas also are undergoing subsidence, erosion and stresses similar to the lower Mississippi. They are also impacted by reductions in the load of sediment that traditionally kept them nourished with fresh soil deposits with every flood. Smith suspects a lot of data exists but is not being collected and interpreted by a universal system or even within individual delta systems because of competing interests and political boundaries.
Smith says the Mississippi delta is probably the most studied in the world and has the special benefit of being overseen by the Mississippi River Commission, a unifying entity established in 1879 that is envied by other world delta regions trying to manage their own rivers and deltaic systems. Most big rivers pass through multiple states or even countries with competing agendas. “By comparison, the Mekong Basin includes six countries, but only four of those are involved in that commission,” Smith says.
“I think the MRC is really a very important approach to looking at this river in its entirety,” Smith says. “When it was founded, the primary goal was flood protection. Then, navigation was added, and now we’re at the point where ecological restoration is certainly included in the bigger picture.”
The issue of sediment starvation, which has led to large-scale wetlands loss in Louisiana, is a charged one. The solution, some engineers say, is to bleed the river during floods, purposefully allowing sediment-laden flows to spread across the land. But it is a scheme that has long met with resistance.
Recently, however, changing priorities and a growing body of knowledge prompted the convening of a Mississippi River Diversion Summit by the Corps in New Orleans in early March. An array of diversion schemes were put on the table. Brig. Gen. Michael Walsh, commander of the Corps’ Mississippi Valley Division and president-designee of MRC, said critical issues to be considered are nutrient availability, channel response, wetland ecosystem design and performance and influence of diversions on the annually appearing Gulf hypoxia dead zone offshore. “The folks in this room are going to help our nation put a path forward on where we are going with river diversions,” Walsh said, adding that the Corps will provide collaborative engineering solutions and a multigenerational commitment to the process.
Collaboration will be a challenge with so many diverse stakeholders, says Garrett Graves, director of Louisiana’s Office of Coastal Protection and Restoration. But, he adds, “we will” do diversions in Louisiana. He believes diversions alone will not be enough to secure the delta for the future. “They are a vital component to sustain our coast in Louisiana, so it’s going to happen,” Graves says.
Because of the need to protect coastal cities and infrastructure against anticipated climate change, delta issues are becoming a focus of world attention and delta stakeholders are starting to come together. The world’s delta regions are not in universal decline, but they are all sliding in the same direction. If global warming progresses, sea-level rise continues as it has for the past 100 years and nothing is done to protect them, the deltas will become increasingly stressed and subject to flooding, both from the rivers coursing through them and the seas at their doors.
As the stakeholders have started sharing notes, they see they have many of the same problems—and they have started sharing solutions. “If you compare deltas to the small islands threatened by sea-level rise in the South Pacific that capture so much attention, there are very few people living there,” says Piet Dircke, water-resources business-practice director for Arcadis in Maastricht, the Netherlands. “Soon, the majority of the world’s population will be living in deltas, if they are not already there now. We need to emphasize the sense of urgency more.”