Water quantity and quality in Ulao Creek have a significant effect on the quality of the Milwaukee River, especially when flooding in the Ulao Creek Basin delivers a large sediment load to the main channel.

While the vegetation of this large wetland ecosystem has been disturbed by a long history of farming and ditching, the hydrology of the wetland system remains largely intact. Ulao Creek has tremendous potential for the restoration of native wetland plant communities.

The Ulao Lowland Forest, a 347-acre locally significant natural area in the Ulao Creek Watershed, has been identified in the "Regional Natural Areas and Critical Species Habitat Protection and Management Plan for Southeastern Wisconsin." Such areas are designated as such so that they can be preserved via protective ownership.

The pre-settlement vegetation of the Ulao Swamp, like that of most other large wetlands in the region, was a diverse mix of white cedar/tamarack conifer swamp, hardwood swamp, shrub-carr, sedge-meadow, wet-meadow, and shallow marsh communities. The complex patterning of these dominant plant communities was undoubtedly correlated with subtle local variation in the hydrology of the wetland. The conifer swamp, which occupied the greatest acreage of the wetland, was long enough from north to south to have been noted in the original land surveyors notes, and therefore to be included on the map of the “Original Vegetation Cover of Wisconsin” (R.W. Finley, 1976).

Before the accelerated degradation accompanying suburban sprawl in the Watershed, the low marshy areas along Ulao Creek provided a spawning area for very large numbers of northern pike. A restored, protected Ulao Creek could return to this important function.

Ulao Creek empties into the Milwaukee River just north of Thiensville. Migrating salmon from Lake Michigan have been shown to travel as far as the Grafton Dam, several miles upstream of the Ulao creek entrance to the River. A cleaner Ulao creek, with more stable flows, would be an enhancement to the migration of the salmon.

Of critical importance for future land use planning and protection of unique natural areas, The Ulao Creek Watershed adjoins an area of lakeshore lands just south of Port Washington. Included in this area is about 2 1/2 miles of largely unspoiled bluff lands, the largest such area left between Indiana and northern Sheboygan County.

Along these bluffs, two ravines lead to Lake Michigan. They contain flowing springs, cedar forests and plant life that has been obliterated in most nearby, urbanizing areas. One close-by natural area, the Lions Den Gorge, is located in the Town of Grafton. The Lions Den, characterized by a deep ravine, leads to Lake Michigan. It is dominated by white cedar and hardwoods, and contains good-quality herbaceous cover, including some northern relicts