Interview with a native plant pioneer: revegetating levees in the Delta

Jeff Hart leading an ecotour of the Delta.In the Sacramento-San Joaquin River Delta of California, there are few investments more precious - and more fought over - than levees.  Levees protect farmland below sea level from inundation and erosion, prevent saltwater intrusion into the freshwater rivers that provide irrigation and drinking water for much of California, and stem the rise of floodwaters during the rainy season.  

They also, unfortunately, often entail the elimination of riparian and marsh habitat when constructed and maintained. Conventional wisdom has decreed that vegetated levees are more subject to failure; tree roots are considered a kind of slow-motion pick ax that weaken levees and make them more prone to failure.

Since the early 1990s, Jeff Hart has been challenging that conventional wisdom, combining research, botanical knowledge, and an array of GIS and other technical Broken levee along the Sacromento River being repaired.skills to revegetate levees with native plants in ways that actually make them stronger.  

After having received a master's in ethnobotany from the University of Montana and a Ph.D. in evolutionary biology from Harvard, Jeff returned to his native California and eventually opened Hartland Nursery, run in partnership with his wife Toni Toban-Hart.   His nursery and innovative planting methods have been used in over 20 sites throughout the delta, including a $1.8-million project funded by the California Bay-Delta Authority to restore several miles of levees in 2003 - 2006.

Jeff agreed to give us his perspective on levee maintenance and restoration, both what's been done and his vision for the future.

CM:  Jeff, I've known you since we worked together at the Cosumnes River Preserve in the early 1990's. Back then you were focused on riparian restoration along the slough channels at Stone Lakes NWR.  Is that what led you to focus on levee revegetation, and can you describe how you first began developing your methods?  

JH: Riparian vegetation is found along both floodplains and levees.  In fact, the two are hardly distinguishable.  Many people believe that levees are just manmade structures.  Often, they are.  The term "levee" is a French word meaning raised ground.  The natural part of levees is understood in the context of their natural formation through the process soil deposition.  During the phase of river flooding, most soil deposition occurs close to the river.  Historically, the highest landforms in the Central Valley landscapes are the levees.  They have the richest soils and the most luxuriant growth of vegetation.  In the process of manmade levee "enhancement", the riparian levee landscape has been altered.  For the most part, these near shore environments have become barren rocky landscapes.  My interest in this habitat zone has been to meet the challenges of providing enhanced habitat values while meeting flood control concerns.

CM:  Your website emphasizes an ecological approach to restoration that also acknowledges the influence of "human altered conditions to the environment."  Can you tell us in a nutshell what your levee vegetation and habitat restoration methods consist of and describe one of your projects for us?

JH: Successful habitat enhancement requires an understanding of current environmental conditions.  Too often those of us on the "green" side have a romantic perspective about how the world ought to be.  This can lead to unsuccessful outcomes as the anthropogenic world in which we live requires meeting new challenges.  This is especially true working along modern levee systems that need to meet several objectives.  In some environments we install more passive bank protection/vegetation systems; in other environments, we acknowledge that the engineer's rock is needed.  

CM:  What types of plants do you use to revegetate the levees and why? Can you tell us why native plants are better for Delta levees? 

JH: Typical riparian plants include oaks, willows, cottonwoods, and a host of understory plants such as perennial grasses and sedges. Native wildlife species have coevolved with native plant species, so they are the best choice for habitat enhancement.  Non-native plants can be invasive (weedy) and costly for management.  The types of plants chosen for levee rehabilitation projects depends on a number of factors.  Small, narrow levees can at least benefit from planting of perennial grasses and related plants.  Wider and more substantial the levees can be planted with larger and more substantial plant communities.  For all of modern levees, a balance needs to be found with the need for levee inspection.  A middle ground, compromise solution would be the planting of modest sized woody plants with grassy understory plants, such that periodic inspections could be done.  The right combination of plants have roots that bind soil, reduce surface energies of moving water, and precipitate deposition of fine grained soil particles.  

CM:  How do you work with engineers who design, construct, or repair the levees?  Do your methods require any unusual levee construction materials?  

JH: We work with engineers in a variety of environments that combine habitat and flood control, levee protection measures.  These can encompass a complete spectrum from planting within existing structures, installation of vegetation erosion control structures, use of erosion control blankets, incorporating special erosion resistant soil mixes that allow for plant growth, and for special rock, protective berms.   We recently designed and built, in coordination with a local reclamation district, "modern" levees that incorporated rock, soil and plants.

CM:  Can you compare the cost-effectiveness of your methods with traditional levee construction and maintenance over the "lifetime" of a levee?  

JH: The presence of vegetation along levees includes both design and maintenance concepts.  Our design concepts that use plants are done at price reductions, from as much as 1/100 the cost to 30% less.  Part of this is due to allowing for the design/build concept to be implemented in a practical fashion.  We have not been influential, yet, with implementing maintenance activities.  Maintenance as practiced today involves removing vegetation, sometimes resulting in levee slope erosion and levee failure.  We believe that the implementation of sustainable, native plant communities would save levee maintenance and flood control costs, but would also be self-mitigating for environmental concerns.  To that end, plants would be considered as a partial solution to problems of levee failure.

CM:  You run Delta ecotourism tours from Hartland Nursery on your boat, the Tule Queen, during the summer.  What is the focus of these trips?  

JH: The California Delta is a hot topic right now.  We give tours to a great variety of interests and perspectives.  Our goal is to provide the public and policy makers with a first hand look at the Delta.  While environmental policy issues are of interest to many clients, we try to make these trips fun, educational, and interesting.  We emphasize issues such as human culture and history and how these perspective intersect the natural and artificial conditions of the Delta.

CM:  What do you believe is needed in the future to maintain both the ecological viability of California's Bay Delta and rivers while at the same time safeguarding the water supply and cropland?  Will something have to give?  

JH: Many different perspectives are given on our ecotours.  Our highly charged political environment is matched locally, regionally and statewide with self interests that often fall along geographical and/or use groups needs for water.  Most groups view the Delta -- its water and resources -- as commodities.  What is needed, in my view, is a perspective of what is good for the Delta on a long term, sustainable basis.  Many outsiders view the Delta under current "management" practices as unsustainable.  I would not totally disagree.  However, few if any aspects of modern "civilization" are based on concepts of sustainability and social justice.  The problems and solutions to the Delta should be dealt with on the basis of sustainability goals and practices on broader regional, national, and global perspective and ones that consider fairness along a broader range of cultural conditions.  For the Delta, there are a number of practices, such as the implementation of a green levees policy, sequestering carbon through re-marshing environments below sea level, and the development of eco and agri-tourism economic models that would greatly help conditions.  

--by K. Gregg Elliott