Detailed Profile

The Lower Des Plaines watershed extends from north central Cook County down through eastern DuPage County and western Cook County into northern Will County.

Major waterways include the Lower Des Plaines River (from the point where the Salt Creek joins it near the Brookfield Zoo), Salt Creek, and portions of the Chicago Sanitary and Ship Canal and the Calumet-Sag Channel.

The 357-square-mile area unites some of Illinois' most affluent suburbs and historically important industrial towns. Twenty-eight Superfund sites, one of them on the National Priority List, are reminders of the area's heavily industrial past.

While the leading economic sector today is services, manufacturing is still prominent, providing almost one in five jobs in 1995.

Human development now covers two-thirds of the area's surface. The basin's one million residents comprise 9% of the state's population and at least one of every ten employed Illinoisans works here.

The landscape of the Lower Des Plaines basin was formed by the last glacial advance that ended about 13,000 years ago.

The region includes some outstanding scenery and geological features such as seeps, ponds and hills formed by glaciers, and dolomite cliffs and canyons eroded into ancient Silurian dolomite more than 400 million years old.

The eastern part of the lower Des Plaines region includes part of the flat basin of ancient lake Chicago and, to the west of that, closely grouped moraines. In the western portion, the moraines were dissected by the rivers of water overflowing from lakes formed by melting glaciers. The northern third of the basin features broader upland areas, level between tributaries and somewhat poorly drained.

The clay-rich local soils tend to absorb water relatively slowly and flooding has been a concern since early settlement. In the last century much of the land has been paved over, exacerbating flooding.

In the southern part of the lower Des Plaines basin, far below the bedrock surface, liesthe massive Deep Tunnel and Reservoir Project, which stores excessive water during storms.

While numerous detention basins have also been built to alleviate the problem, preserving and restoring wetlands is a priority to slow runoff.

A relatively large portion of the area has very thin soils. Romeoville Prairie and lockport Prairie Nature Preserves show the distinctive meld of wetland communities that thrive in these shallow-soil areas. A tapestry of wet- to mesic-dolomite prairie, marsh, sedge meadow, fens, floodplain forest, and a high-quality spring can be found at the preserves.

In its lower basin the Des Plaines River flows in a channelized course parallel to the Sanitary and Ship Canal. North of lockport, the river's channel is flanked by 80-100 foot natural bluffs within 2,500 feet of each bank of the river, reminders of this section's past as the key drainage point for ancient lake Chicago.

Salt Creek remains less naturally well defined in its valley, and is a source of more persistent flooding problems for suburbs now along its banks.

There are 18 lakes in the region greater than 20 acres - some of them naturally occurring, some manmade - with hundreds more small lakes and ponds, most under two acres each. Most of the larger lakes in the southern lower Des Plaines area are former quarry pits.

Approximately 10,633 acres of wetlands remain in the area, about 21 % of the presettlement amount. Disappearing with the wetlands were the nesting areas of now rare bird species such as the pied-billed grebe, the American bittern and least bittern, the black-crowned night-heron and yellow-crowned night-heron, the northern harrier, king rail, common moorhen, black tern, and yellowheaded blackbird.

Despite rapid development, there are still some 7,500 acres of nonforested wetlands in the basin, including notable marshes and sloughs in the Palos Preserves, in forest preserves in the Schaumburg-Elk Grove Village area, and at Campbell Slough near Addison.

Sixteen amphibian and 22 reptile species are known or likely to occur here, 39% and 37% of the state's amphibian and reptile species, respectively. These include the state endangered spotted turtle and Blanding's turtle as well as the state threatened Kirtland's snake.

Because urban pollution has degraded the habitats of aquatic species such as fish and mussels, the basin has a low diversity of aquatic life today. While records show 49 species of fish, 31 of mussels, and 10 of larger crustaceans, some species have disappeared in recent decades. Mussel populations have become very small, with only one of the 31 species having been collected in the past 20 years.

Up to 1996, the IEPA had assessed 213 river miles in the watershed and rated them as being good or fair. Fourteen percent were found to meet the needs of designated uses, about half were impaired to a minor degree, and 17% were severely impaired. of 13 Lower Des Plaines subwatersheds prioritized by IEPA, 11 - including the Des Plaines and Salt Creek - were identified as restorable.

The basin retains a relatively high number of now-rare plant species. There are 10 state-threatened, 15 state-endangered, three federally threatened, and one federally endangered plant species in the valley. Most of these plants live in prairie and wetland habitats.

A dozen high-quality natural sites, totaling some 516 acres, have been identified in the basin.

More than four-fifths of the basin was covered by tallgrass prairie at the time of Euro-American settlement, but only small acreages of highquality prairie remain in the region today. About half of this is categorized as mesic prairie, which grows in moderately wet soil and was originally only a small percentage of the whole area.

Wolf Road Prairie boasts a species list of 320 plants and includes the only remaining high-quality undegraded mesic prairie found in the basin.

Other types of high-quality prairie preserved in the Lower Des Plaines basin include one acre of dry-mesic gravel prairie and four acres of mesic gravel prairie (22% of all that remains in the state) at Santa Fe Prairie Nature Preserve. The preserve hosts more than 250 native plant species-the variations in soil moisture support far greater diversity than would generally be expected of a site its size.

Examples of rare dolomite prairie can be seen near Lockport and Romeoville. Dolomite prairie occurs where dolomite is usually less than a few feet below the soil surface. Only 42 acres remain in the state; most sites were either destroyed by quarrying for flagstone or mining for gravel. The lakeside daisy, a federally endangered species that is unique to this type of prairie, is only found at one location in Will County, where it has been reintroduced into the Lockport Prairie.

Unlike prairies, forests today cover more of the land than they did at settlement. Approximately 16.5% of the area was once forested; now about 19.4% (44,430 acres) is forested, but only about 432 acres are high-quality and undegraded. About 94% of the forest is upland forest.

Northern flatwoods in Illinois are found on poorly drained sites within the Valparaiso Morainic System,
largely within this basin. A total of 31 acres of high-quality northern flatwoods (36% of the statewide total) have been identified at a single site here.

The basin's natural history of rich prairie, wetland and forest resources made it a haven for birds, with 150 species recorded as breeding in the basin. Today, however, 61 of these are either locally extinct or rare during the breeding season, probably due to loss of habitat.

Despite the fact that two-thirds of the area is developed, some resilient species have expanded their numbers in recent decades. White-tailed deer, coyote, and raccoons have thrived as suburban residential areas and parklands have replaced industrial and agricultural land. (Farmland declined from 46% of the basin's land cover in 1925 to 16% today; manufacturing employment fell by 12% since 1980.)

Other mammals that do well in urban areas include the Virginia opossum, eastern cottontail, fox and gray squirrels, red fox and striped skunk. The area is also home to eight species of bats, 19 rodents, and five insectivores.

Between 1970 and 1990, population in northeastern Illinois grew by about 4%, yet acres of developed land increased by about 50% and now cover 66% of the land. Residents have responded to the speed and size of the changes, and the basin has become a national leader in nature preservation and restoration.

As early as the post-Civil War era, Frederick Law Olmsted helped design what has since become a federally designated landmark, the town of Riverside. The wooded curving streets and common park areas incorporating the river, sought to combine human culture and nature. It showed future generations how development and a sense of place could be nurtured together.

A century ago, Jens Jensen, Dwight Perkins and other Chicago-area conservationists helped establish a ring of preserves around Chicago, including the landmark corridor of forest preserves along the Des Plaines River and Salt Creek.

Today about 10% of the area's land (23,202 acres) is set aside as county conservation areas, forest preserves, etc. In addition, 16 state nature preserves and 29 state natural areas have been established within the watershed.

The Illinois & Michigan Canal National Heritage Corridor, designated in the 1980s, was the first of its kind in the nation. It stretches from La Salle-Peru in the west to Lake Michigan in the east. The heart of the corridor lies in the Lower Des Plaines basin. The corridor helped stimulate the growth of other "greenway" projects in the basin, such as the Salt Creek Greenway Project and the Northeastern Illinois Regional Water Trail Plan.

Current residents are looking at the Lower Des Plaines basin and at their place in it differently from previous generations. They see what makes the area distinctive, and have set about trying to save those special features.