Sustainable Shorelines Project:
Mitigating Shoreline Erosion along the Hudson River Estuary’s Sheltered Coasts
Betsy Blair – April 24, 2009
Background
The Hudson River Estuary’s 300-mile shoreline has been dramatically altered over the
last 150 years in order to support industry and other development, contain channel dredge
spoils, and to withstand erosive forces of ice, wind, and waves. During the summer of
2005, Hudson River NERR (National Estuarine Research Reserve) staff mapped and
classified both shorelines along a 125-mile section of the Hudson River Estuary, from the
Tappan Zee Bridge to Troy (Miller, Bowser, and Eckerlin, unpublished). About half of
the natural shoreline has been engineered with revetment, bulkhead, or cribbing or
reinforced with riprap. Many shorelines contain remnant engineered structures from
previous human activities. The remaining “natural” shorelines (which however have
been affected by human activities such as disposal of dredge spoils, invasive species, and
toxins) include a mix of wooded, grassy, and unvegetated communities on mud, sand,
cobbles, and bedrock.
Sea-level rise and other effects of global climate change provide a strong impetus for
advancing the state of our knowledge of shoreline modifications, their associated
impacts, and the full costs of these (NRC, 2006). Recent estimates for New York City
(Columbia University) project that sea level may rise as much as 12-23 inches (or 41-55
inches, if you factor in rapid ice melt) by the 2080s. Rises of this magnitude will lead
property owners along the tidal Hudson and other coastal waters to either build, repair, or
modify structures along the shore to protect their properties (Titus et al. 1991, Nicholas et
al. 1999, Titus and Richman 2001), or to choose alternative strategies. In order to
advance public discourse, policy-making, and individual decision-making, we must
estimate the potentially high costs of damage to structures, lands, and ecosystems
associated with proceeding “business as usual” with shoreline development, the costs of
creating ever-higher barriers to inundation, and the costs of alternative approaches.
This proposal identifies a six-year program of research, analysis and outreach that will
provide a better understanding of the tradeoffs associated with using existing erosion
prevention measures, including shoreline hardening, land management, and vegetative
approaches, to protect the Hudson River Estuary’s sheltered coastlines from the impacts
of rising sea levels, increased storm surges, and waves over the next fifty years. These
coastlines include bluffs, rock outcrops, tidal wetlands, mudflats and sand flats, and
hardened shores. We will identify options for promoting effective erosion control while
preserving, enhancing, and restoring ecosystem functions. The project will focus on both
sides of the northern 125 miles of the Hudson River Estuary, from the Tappan Zee Bridge
to the Troy Dam.
This project will complement and be integrated closely with several regional climate
change response and ecosystem protection initiatives, including the Nature
Conservancy’s Rising Waters Initiative, the New York State (NYS) DEC’s Hudson River
Action Plan, the NYS Climate Change Office, Sustainable Hudson Valley’s Partnership
for Municipal Response to Climate Change, and the New York Oceans and Great Lakes
Ecosystem Initiative. This will be achieved through the work of a sub-group of the
leaders or key players of these closely related initiatives. These leaders are already
working together to insure tight inter-project coordination, in large part through cross
participation in each others’ initiatives.
We have completed significant work to date on the topics of Hudson River Estuary
shoreline status, erosion control alternatives, and stakeholder needs. As described above,
in 2005, the Hudson River NERR mapped and classified the shorelines of the tidal
Hudson River from the Tappan Zee Bridge (river mile 25) to the Troy Dam (river mile
152). Also in 2005, the Hudson River NERR commissioned a study of “soft” engineered
(primarily vegetated) shoreline stabilization alternatives appropriate for the climate and
physical setting of the Hudson River Estuary. This resulted in a final report: Hudson
River Shoreline Restoration Alternatives Analysis (Allen et al., 2006). A survey was
developed and administered to assess our priority audiences’ (engineer, technical
consultant, regulator, and coastal manager) states of knowledge, information needs, and
learning preferences. The report and the survey were the basis for developing a one-day
technical workshop (March 23, 2006) organized under the Hudson River Estuary
Training Program by the Hudson River NERR, with support from the NYS Coastal
Management Program and the Hudson River Estuary Program.
Project Goals
Goal 1: Determine the tradeoffs in “ecosystem services” that arise from the application
of land use management, shoreline hardening, and vegetative approaches to erosion
control.
Although surprisingly little is known world-wide about the ecosystem services associated
with shorelines and shoreline mitigation techniques, we are well equipped to address this
in the Hudson River Estuary. We will build on recent work by members of this team and
others to characterize key biotic, chemical and physical functions or “ecosystem services”
of two important near-shore communities: tidal freshwater marshes (Findlay et al., 2002)
and submerged aquatic vegetation (SAV) beds (Nieder et al., 2004; Findlay et al., 2006).
With Hudson River NERR funding, David Strayer of IES (the Institute of Ecosystem
Studies) is reviewing and summarizing ecological literature about “ecosystem services”
and functions performed by shorelines. IES and Hudson River NERR research staff,
under separate funding, will compare current functions of six types of shoreline with
respect to physical attributes and habitat functions of selected biota. This information
will inform our understanding of ecosystem tradeoffs of existing methods to control
shoreline erosion in years 1 & 2 of this project; we anticipate that the work will raise
additional questions about shoreline functions that we may seek to address in years 3-6 in
order to refine our understanding.
Goal 2: Determine the short- and long-term costs of different erosion prevention
measures, using long-term (50- to 100- year) forecasts of erosion control performance in
the context of sea level rise.
We will seek to quantify long-term costs and impacts, as broadly defined in the CICEET
RFP, associated with different erosion control scenarios through the work of a multidisciplinary team that will focus on two things: refining estimates of storm frequency and
storm severity for the Hudson River Valley; and projecting short and long-term costs and
impacts (as identified in the RFP) associated with vegetated, hard engineered structures,
and land management measures. We will participate in Rising Waters, a climate change
scenario development process will inform our selection of 6-10 erosion control options
on which to focus.
Art Degaetano (Cornell University), who was part of the Northeast Climate Impacts
Assessment (NECIA) team, will seek to refine the NECIA estimates of storm frequency
and storm severity to inform our assessment of costs. Stevens Institute of Technology
engineer Jon Miller and colleagues will identify the short and long-term viability, costs,
and impacts of different engineered erosion prevention measures in the Hudson River
Estuary given forecasts about climate change impacts on sea level and storm surges.
Several team members will work together to evaluate land management approaches for
their potential to influence shoreline erosion vulnerability and promote erosion control,
including planning actions, such as zoning or managed retreat; regulatory measures, such
as buffers, setbacks, or construction standards; incentives; and land acquisition, among
others (NRC, 2007). Tradeoffs in ecosystem services and the short and long-term costs of
these will be characterized.
We anticipate that development of these costs will be an iterative process as we gain
more insight through the course of the project into regional climate predictions, flood
risks, ecological services, and factors that we identify as important drivers for decisionmakers.
Goal 3: Transfer new knowledge and tools to relevant stakeholders.
We will devote a significant amount of time to planning how best to transfer new
knowledge and tools to relevant stakeholders. Our highest priority shoreline protection
decision-makers include property owners, experts and consultants, government
regulators, and policy- and law-makers. We will identify and survey these decisionmakers to characterize their knowledge, attitudes, information needs, and training or
outreach preferences. To identify shoreline landowners, we will use tax parcel maps;
additional data about them will be gained by overlaying the tax maps via geographic
information system (GIS) over the Hudson River NERR shoreline type maps. We will
survey a representative subset of them to obtain information about their knowledge of
climate change trends and shoreline erosion control measures, planned shoreline
management practices, motivations for management, and receptivity to and preferences
for outreach.
Many of the other stakeholders -- experts and consultants, government regulators, and
policy- and law-makers -- have been previously identified by the Hudson River NERR
training staff for workshops, surveys, needs assessments, and focus groups; however the
database of such individuals will be updated and expanded. From our experience, we can
generally say that decision-makers like to receive new information at workshops, which
should include case studies and field site visits, and through written material including
websites and reports. However, we will conduct needs assessments to gain more specific
information about how these audiences will best receive and use technical, scientific, and
economic information. Lastly, we will develop and implement a communications and
outreach plan that factors in all preceding information and that engages partners within
and beyond the shorelines project.