EDITORIAL:
THE CHALLENGES AHEAD
Reinhard E. Flick, Ph.D.
STABILIZATION OF RAVINES, ADJACENT BEACHES
AND BLUFFS ON LAKE MICHIGAN
Charles W. Shabica, Ph.D., P.G., James R. Jennings, Ph.D., P.G., Maynard Riley, and Jeff Boeckler
This report details the performance of four Illinois coastal restoration
and stabilization projects constructed and monitored
over 3-15 years. All include integration of native plants with
stone into sustainable systems that protect ravines and adjacent
coastal beaches from the intense erosional forces of stormwater
runoff and storm waves. Prior to urbanization, ravines were
metastable and bluffs and beaches eroded slowly. All supported
unique plant communities. During the last 125 years, coastal
and ravine erosion has accelerated due to loss of protective
beaches and an increase in peak stormwater runoff flowing
into the ravines. Most of these problems can be attributed to
construction and maintenance of harbor entrance channels,
impervious structures in the watershed and to the introduction
of invasive plants like silver maple and buckthorn. Societal
response has typically been to attack the coastal problems with
hardened structures of wood, steel and concrete and ignore the
problems in the ravines. The result is a lakeshore dominated
by hard defensive structures including revetments, groins and
seawalls, and ravines with a patchwork of retaining walls, storm
sewers, and outfalls. Plant communities have been displaced and
many of the structures have failed, in most cases due to flanking
or foundation failure. This study quantifies the performance of
alternative systems designed to function in concert with natural
processes as compared to hardened erosion control structures.
Study sites include ravines and beaches in fully urbanized areas
of Lake Bluff, Highland Park and Glencoe, and eroding bluffs
at Foss Park Beach in North Chicago. Systems were monitored
for bacterial indicators of sewage pollution (E. coli bacteria),
establishment of vegetation, and erosion and sediment loading
to Lake Michigan. The most successful ravine projects include
removal of invasive plants, restoration of appropriately-sized
stream boulders and cobbles (stream armor) with streambanks
and ravine slopes further stabilized with stone and native plants.
Although water quality improved with reduction of fine sediments
and repair of broken sewers, bacterial monitoring was
inconclusive. Levels of E. coli bacteria were typically high in
the ravines and beach sands and low in Lake Michigan, and
appear to be due to diverse animal communities living in the
ravines and not necessarily human sewage. Except for periods
after heavy rains, the ravines had no effect on E. coli levels in
the lake. The lakeshore adjacent to the ravines was successfully
stabilized with rocky headlands and pocket beaches, wetlands,
and native plants. Results of this report are intended to help
planners better manage Great Lakes ravines and coasts with
techniques that reduce erosion and restore diverse ecosystems.
Based on criteria developed in this study, the Illinois Department
of Natural Resources in cooperation with the Lake Michigan Watershed
Ecosystem Partnership and Alliance for the Great Lakes
has mapped all Lake County ravines to quantify stability and
ecological viability. It is anticipated that with the success of the
ravine mapping project, mapping the Lake Michigan shoreline for stability and ecological viability will soon follow.
USE OF HUMIC ACID AMENDMENT TO ACCELERATE THE ESTABLISHMENT OF DUNE AND BACK-BARRIER MARSH VEGETATION
Jonathan M. Willis and Mark W. Hester
Major limitations to the successful restoration of coastal dune and back-barrier salt
marsh plant communities systems are the often relatively low nutrient and organic
matter content of the substrate. An additional complexity of restoration efforts in these
systems results from concerns regarding the use of traditional inorganic fertilizers
due to the proximity of coastal waters. The use of naturally based products, such as
liquid composts and humic acid extracts, as a means of ameliorating marginal soils
has been increasing in recent years. The potential growth benefits of humic acid on
two dune grasses, Panicum amarum and Uniola paniculata, and two salt marsh species,
Spartina alterniflora and Avicennia germinans, were evaluated in greenhouse
studies under different environmental stressors. Humic acid amendment stimulated
the growth of Panicum amarum and Spartina alterniflora, although no benefit was
discernable for Uniola paniculata or Avicennia germinans. No interactions of stressors
with humic acid amendments, which might have indicated stress amelioration
were noted. These findings suggest that humic acid amendment could be an effective
technique in coastal habitat restoration of targeted species, particularly when the use
of inorganic fertilizer is limited. However, further research will be necessary to better
resolve amendment levels and to optimize benefits under field conditions.
MONITORING OF RECENT MORPHOLOGICAL CHANGES OF THE DUNE OF VOUGOT BEACH (BRITTANY, FRANCE) USING DIFFERENTIAL GPS
Serge Suanez, Jean-Marie Cariolet, and Bernard Fichaut
The dune of Vougot beach is a massive drifting sand body approximately
250 to 400 m wide and 2 km long. It is located in
the municipality of Guissény, on the north coast of Finistère
(Brittany). This dune, with a southwest to northeast position,
protects a vast polder area which was disconnected from the
sea by a dike construction in 1834. For several decades the
eastern part of this dune experienced erosion mainly due to
the construction of an artificial jetty in 1974 (Curnic jetty),
which entirely modified the hydrodynamics and sedimentation
processes. In order to determine the actual trend of evolution,
the advance rate, and the resultant sand drift that is occurring,
a survey of the dune was achieved between 2004 and 2009.
Shoreline changes were monitored on a yearly basis; in addition,
two detailed topography surveys (2005 and 2009) were
carried out. Topography surveys were made using a Trimble
DGPS respectively with 5 cm and 1.5 cm of horizontal and
vertical accuracy. ArcView GIS was used to process the data
and display the results. Shoreline change rates were determined
using Digital Shoreline Analysis (DSA) ArcView tools to
measure erosion and accretion transects. 3D surface analysis
was based on Digital Elevation Model (DEM) calculations
using Surfer software. Foredune changes showed that dune
evolution since 2004 is in accordance with the trend observed
during the last decades. However, the speed of dune retreat has
increased from 0.6 m/yr to 1.5 m/yr. The comparison between
DEMs obtained from the 2005 and 2009 surveys confirmed this
evolution. A volume of eroded sand from the dune amounting
to -10,677 ± 110 m3 with an erosion of the foreshore beach of
-10,933 ± 1,396 m3 was determined. These results confirm the
fact that the Curnic jetty is constantly interrupting the sand
drift inducing an increase in sediment loss from the Vougot
beach/dune system.
O’BRIEN AWARD WINNERS:
AN INTERVIEW WITH BILLY EDGE
Beth Sciaudone, Ph.D.
COASTAL OBSERVATIONS:
SOUTH NEW JERSEY
Andrew Morang, Ph.D.
COASTAL OBSERVATIONS:
TSUNAMI WARNING SIGNS ON THE ENSHU
COAST(JAPAN)
Hubert Chanson
THE AMERICAN SHORE AND BEACH PRESERVATION
ASSOCIATION THIRD ANNUAL PHOTOGRAPHY CONTEST
THE SECOND ANNUAL ASBPA PHOTO CONTEST WINNERS
ASBPA 2010 NATIONAL COASTAL CONFERENCE
CALL FOR PRESENTATIONS |
