During the past two centuries the Illinois River and its hydrology have been altered numerous times. Early navigation works, levees, diversion, agricultural and urban drainage practices, locks and dams and other changes all contributed to habitat modification. Over the years the river has changed from a free flowing stream bisecting a broad floodplain to a series of pools with substantial areas of leveed floodplain. The image conjured by the term “restoration” varies with the time frame used as a base. Given that all major navigation dams were in place by the1940's, a common vision of a restored river includes permanently flooded lakes and
backwaters with sufficient depth to support the flora and fauna which were abundant in the early 1950's as well as recreational boating. Others envision a relatively free flowing river with a variety of backwater and side channel habitats.Ope

Marlin, John C.

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224BACKWATER RESTORATION OPPORTUNITIES: ILLINOIS RIVERJohn C. MarlinWaste Management and Research Center, Illinois Department of Natural ResourcesOne E. Hazelwood Dr., Champaign, Illinois 61801E-mail: jmarlin@wmrc.uiuc.eduDuring the past two centuries the  Illinois River and its hydrology have been alterednumerous times.  Early navigation works, levees, diversion, agricultural and urban drainagepractices, locks and dams and other changes all contributed to habitat modification.  Over theyears the river has changed from a free flowing stream bisecting a broad floodplain to a series ofpools with substantial areas of leveed floodplain.  The image conjured by the term “restoration”varies with the time frame used as a base.  Given that all major navigation dams were in place bythe1940's, a common vision of a restored river includes permanently flooded lakes and backwaters with sufficient depth to support the flora and fauna which were abundant in the early1950's as well as recreational boating.  Others envision a relatively free flowing river with avariety of backwater and side channel habitats.  A realistic concept will attempt to provide the habitat diversity necessary to support thehistorical species within the constraints of a navigation system and other economic and socialfactors.  Backwater restoration and that of the main stem can be driven by determining whichimportant habitat types are most degraded or in limited supply and seeking to protect or recreatethem.  For example, the river has limited fast flowing or riffle habitat.  This fact makes therapidly flowing area below the Marseilles dam particularly valuable and worthy of protection. Likewise, relatively deep water off the main channel has virtually disappeared in recent times.  On the other hand, shallow water,  mudflats and willow covered floodplain abound, althoughtheir habitat value is degraded by unnatural water level fluctuations.  Historic maps of the river valley can guide restoration efforts.  They  show areas whichhistorically were water, marsh or land.  For example, while the Peoria Lakes have been floodedsince the 1940's, topographic maps show that in the 1890s they had substantial areas of marshand several large islands downstream of Spring Bay (Fig.1).  The area of the lake between SpringBay and Chillicothe included large amounts of marsh as well as farmed land and roads (Fig. 2 ).   The area from Chillicothe to Lacon was largely marshland with some permanent lakes andconnected backwaters (Fig. 3), while Lake Senachwine was mostly marsh with connectedbackwaters.  The reach between Chillicothe and Lacon will be emphasized in this paper as itillustrates several points.  The Woerman maps were produced by the Corps of Engineers in 1903 and show theriver and floodplain during low water after Diversion from Lake Michigan began in 1900.   Thehigher water levels expanded the area of backwater lakes and side channels.  Fig. 4  showsMeadow Lake above Chillicothe in an area shown as marsh in the 1890s.  Likewise  Fig. 5 shows enlarged Wightman and Gar Lakes near Lacon in 1903.By comparing the historic maps with current topographic maps and satellite imagery it ispossible to identify areas which may be most suitable for restoring particular habitats.  Forexample, sediment removed to restore depth could be placed on old island sites or shallow areaswhich would provide a firm base to support the material.  Similarly locations that were water onthe old maps  are likely spots for dredging deeper pools.  They are filled with relatively softsediment which is more readily removed than original floodplain soil and less likely to containstumps and other debris.  Areas that were never deep are likely candidates for wetland, marsh225and moist soil habitat restoration, and elevated habitat for mast producing trees. By comparing maps using GIS technology it is possible to see where sedimentation hasbuilt up land over the past century.  They also indicate where sediment deposits in today’suniformly shallow backwaters are deepest.   Figures 6 and 7 show  Meadow Lake and Wightman and Gar lakes respectively.   Thefigures show the 1903 Woermann map superimposed on the topographic map based on 1970aerial photography.  The small black dots depict soundings taken in backwaters for theWoermann maps, and indicate historically deeper water.   On the superimposed maps the darkgray areas were water in 1903, including the main channel.  The heavy line indicates the extentof water on the topographic map.  This additional area was originally marsh or elevatedfloodplain before the navigation dams raised the water level.  At that time Gar and Whightmanlakes were joined.   Note there are small islands and peninsulas on both figures.  Areas where theWoermann soundings overlay water in figures 6 and 7 are likely locations where sediment couldbe readily  removed from the backwaters to restore areas that were historically deep. Figures 8 and 9 are satellite photographs of Meadow and Wightman lakes taken in thefall of 2000 (1903 sounding data is superimposed on the Meadow Lake photo).   The photosclearly show that the peninsulas in both areas have greatly expanded due to sedimentation andnow encompass the former small islands.   A new island is forming in Wightman Lake.   Thesounding dots from the Woermann map are superimposed on Meadow Lake.  It is apparent thatthe original area of Meadow and Wightman Lakes are still covered by water, but that much ofGarr Lake is now covered by accumulated sediment.  Inspection at ground level confirms thatwillows are invading this new land.  Goose Lake to the right of the Lacon Bridge has shallowwater over its once deep areas.  Historic maps of other sections of the river mainstem show where islands and otherfeatures have existed since the 1800s.  Restoration of water depth and relative land elevation inthese areas could significantly increase habitat diversity.  Environmental Management Program (EMP) projects on the Mississippi and IllinoisRivers have successfully restored selected island, backwater and wetland habitat and areproviding useful insights for large scale restoration.  DNR is conducting some small pilotprojects on habitat restoration techniques using sediment removal and placement technology.  One project involving geotextile tubes and a new dredge which uses a displacement  pump tomove sediment without adding water was demonstrated at the Woodford County State Fish AndWildlife Area near Chillicothe in May of 2000.  Figures10 through13 show the construction of asmall island  as part of that project.  Figures 14 and 15 show island building with a conventionalclam shell dredge. Knowledge of the Illinois River valley’s physical and biological history combined withinformation gained from pilot projects will provide the basis for future restoration projects.  ACKNOWLEDGMENTS Various assistance was provided by Kress Corp.; Caterpillar Inc; Illinois State WaterSurvey, Illinois Geological Survey, Illinois Department of Natural Resources; the Rock IslandDistrict, USACE; Wisconsin DNR; J.F. Brennan Co. Inc.; Midwest Foundation; Mike Duke; andJack Fowler among others. This paper is adapted from a powerpoint slide  presentation given at the Governor’sConference on the Management of the Illinois River in October 4, 2001. 226Figure 1.  This topographic map from about 1890 shows Up per Peoria Lake between the narrows andSpring Bay (lower right).   T he Stippled area is marsh a nd three islands are clearly visible.  The islands,marsh and some floodplain were covered with water by the navigation dam.  Sediment  removed to deepenthe lake cou ld be plac ed on the o ld islands resto ring both aq uatic and island  habitat.  Figure 2.   Upper Peoria Lake near Rome and C hillicothe in the late 1890s was largely a marsh.  Roads andfarm fields were covered with water by the navigation dam.  Much of this area was subject to frequentflooding, esp ecially in the spring .   227Figure 3.  In 1890 the area between Chillicothe and Lacon (lower right) was largely marsh and low lyingfloodplain.  Several permanent backwaters existed, some of which were connected to the river even at lowwater.  During most years the natural flood cycle provided fish spawning habitat on the floodplain in thespring.   W hen flood w aters reced ed,  moist soil p lants favored  by waterfowl g rew on mu dflats and aq uaticplants thrived  in the marshes .  The natura l flood cycle ha s been disru pted to the d etriment of ma ny species.  M marks the spot now occupied by Meadow Lake, while W and G are on Wightman and Gar Lakesrespectively.Figure 4.  The water level rose when water was diverted from Lake Michigan in 1900.  This figure from aWoermann map  shows Meadow Lake at low water after diversion.  The dark areas are permanent water andthe lines are on e foot conto urs.  The m ain channel is a t the bottom .  228Figure 5.  T he Wo ermann m ap near La con show s Wightm an Lake (W ) and Ga r Lake (G ) as perma nentlyconnecte d backw aters.  Goo se Lake is the d ark area in the  upper righ t.Figure 6. When the  Woermann map is superimposed on the topographic map (Chillicothe quadrangle,1972, based on 1970  photography) the influence of the navigation dam becomes apparent.  The dark grayareas were  water in the ear ly 1900s.  T he light gray area  outlined by the  line marked  NP (no rmal poo l) isthe extent of the water surface in 1970.  Note the island (I) and peninsula (Pn) forming as a result ofsediment d eposition.  229Figure 7.  The superposition of the Woermann and topographic maps of the Lacon area (Lacon quadrangle,1972) show that Wightman and Gar Lakes were joined when the dam  raised the water level, althoughsediment islands were forming in the Gar Lake area by 1970.   Much of the lower end of Goose Lake (GL)was still covere d by water in 1 970.  T he dots on  the Wo ermann m aps marke d soundin gs in the back waters.  Figure 8.  This is a landsat photo taken in the fall of 2000 with the Woermann map soundingssuperimposed.  It shows that most of the deeper parts of Meadow Lake that were water prior to the dam arestill covered with water.  However, the peninsula shown on the 1970 map has grown and merged with theisland. Me adow La ke appe ars to be a go od cand idate for resto ration as a co nnected b ackwater.  230Figure 9.  A  fall 2000 photo of the Lacon area shows that the Wightman Lake remains as water while muchof Gar La ke is filled with sedim ent that forms a la rge peninsu la.  This loca tion could a lso suppo rt a varietyof restored  habitats.  Figure 10 .  Small geote xtiletubes were placed in UpperPeoria L ake near C hillicothe inthe Spring of 2001.  When filledwith sediment the tubes formeda small trapezoidal island.  Thetubes are intended perform like aberm, ho ld the sedime nt inplace, and prevent it from beingeroded by wave action.231Figure 11.  The Dry Dredge shown herelifts sediment from the lake bottom anduses a displa cement pu mp to mo ve itwithout adding water.  The pump filledthe geotubes with sediment and thenpumped sediment with the consistency oftoothpaste behind the tubes to form asmall island.  The island was filled onMay 2.  Figure 12.  Engineers are shown standingon a tube taking samples on May 22.  Thesediment developed dessication cracksalmost immediately and consolidatedrapidly.  Despite high water, whichflooded the island during most of June,researche rs could wa lk on it in early July. Figure 13.  A DNR site manager standson a geotu be in Augu st.  The sed iment iswell consolidated and supports volunteervegetation.  Plants began growing on theisland after the first week, but weregenerally eaten by waterfowl or killed byhigh water.   T he geotub es successfullyprotected the island from erosion duringthe summer and fall, despite frequentwater level fluctua tions and high  winds.  232Figure 14.  A conventional clamshell bucket was used during high water to gently remove sediment andcreate sma ll islands in severa l locations on  June 12.  T he sedime nt was disturbe d as little as possib le topreserve its stru ctural integrity.Figure 15 .  By July 7researche rs could wa lkon the clamshelledislands.   By observingthe  small  islands,researche rs will gaininsights useful forbuilding large islandsand developingsediment handlingtechniques fo r IllinoisRiver restorationprojects.  

Backwater Restoration Opportunities: Illinois River

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Backwater Restoration Opportunities: Illinois River

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