Riparian Buffers 2: The Lehigh Parkway

“Allentown is especially favored with a wealth of natural beauty, having five water courses run through its corporate limits. General Trexler in his lifetime strongly recommended that these streams should be controlled by the city and their banks landscaped to provide a protected watershed for the city’s supply.” – Trexler Estate Review 1945

Before getting to the actual Riparian efforts in the Lehigh Parkway, I want to share some information with you about the Little Lehigh Creek. From the Coldwater Heritage Partnership 2007 report on the state of the Little Lehigh Creek:
“The majority, or 56 percent, of the Creek’s main stem is in poor condition (nearly 14 miles.) Thirty-two percent (7.6 miles) is in fair condition. No reaches received an overall score in the excellent category.
A total of 27 reaches out of 168 scored poorly. This low score means there is little or no vegetation along the stream, or the riparian area has been mowed to the edge.
The majority of the reaches that scored poorly are located in the Little Lehigh Parkway, Allentown, where the creek has been made accessible to recreational users and often mowed to the edge.
This area has many mature trees but they are not planted densely enough to function as a forest.
A golf course property did not score well as vegetation and woodlands close to the playing area are seen as a hindrance to golf play where the course winds along the creek.
The 27 reaches in poor condition contained three or less types of cover and often no trees or shrubs along the bank, and no boulders or cobbles were present in the stream channel. The portions of the creek that offered less than ideal habitat conditions were found throughout the watershed.
The Department of Environmental Protection determined that stream bank instability leading to siltation is the number one factor impairing streams in Pennsylvania. This condition threatens the viability of the Little Lehigh as a source of drinking water.
The Little Lehigh Parkway offers excellent creek access to the detriment of fish and other aquatic life. Forty-one reaches scored in poor condition for aquatic insect habitat, contained two or less types of habitat, and had few rocks since much of the original stream bottom had been buried under sentiment. Often there were few trees and shrubs present along the creek reducing the amount of leaves in the stream, an important food source for aquatic insect larvae.
Upstream and downstream reaches can be more ecologically managed with large stands of trees and plantings left intact. This balances the negative effects of numerous recreational park users with the ecological needs of the creek. Trees and plantings assist in protecting the viability of the Little Lehigh as a source of drinking water.
A creek not functioning properly will contain trees with exposed roots. Over time trees will fall into the creek. Normally, the network of roots from a mixture of trees, shrubs, grasses and wildflowers stabilize the banks effectively. (Some areas of the Little Lehigh in the City of Allentown have lost up to one foot a year for several years of stream bank because there are too few roots to keep the soil in place during heavy storm water flows.)
All of these factors enhance siltation, sediment buildup and other stream degradation which threatens the viability of the Little Lehigh as a source of drinking water. “

Given those results and coupled with the fact that the Little Lehigh provides drinking water (after treatment) to 130,000 people here in the city, it is obvious that General Trexler’s wishes for our watershed have not been followed.

This is beginning to change however and Riparian buffer efforts are underway in the Parkway. The vast majority of the creek is still without significant Riparian zones but next to the Robin Hood Bridge a restored area is flourishing and “no-mow” zones are beginning to crop up.










I am very glad that these efforts are underway here and in our other parks. The consequences of not establishing these Riparian zones would be staggering to our local ecosystem. Much much more still does to be done. It is my belief that these projects are of the utmost importance and will positively affect our parks many times more than any other renovation efforts would.

There are still more areas to investigate and the next Riparian post will focus on the need for non-invasive plants and what our native plants are and look like.