Rivers + Streams
The rivers and streams of the Lehigh Valley have played an important role in its history and development. The area’s three cities and some of its major boroughs grew along the banks of the Lehigh or Delaware rivers. The Lehigh and Delaware Navigation Canals owed their existence to these rivers. Many streams served as the sites for early mills that were dependent on a supply of running water. Most major industries also were located along the banks of rivers or streams. Visually, rivers and streams provide some of the most scenic settings in the region. A top example of this is the Delaware River Scenic Drive that follows Route 611. The multitude of recreation activities associated with waterways is high on the list of important regional assets. The Lehigh and Delaware rivers provide boating and fishing opportunities. Many trails in the Lehigh Valley are located within river and stream corridors. For instance, the 165-mile D & L Trail, extends from Bristol Borough in lower Bucks County to Wilkes-Barre. Rivers and streams either serve, or have the potential to serve, as linkages between recreation areas. Waterways also provide critical wildlife habitat. Many species of birds, aquatic animals and mammals depend on river and stream corridors for travel, cover and nesting places. Finally, high quality rivers and streams are of critical importance for the preservation of water supplies in the Lehigh Valley.
High-quality rivers and streams are of critical importance for the preservation of wildlife and the recreational opportunities they support. Recognizing the importance of water quality to the preservation of Pennsylvania’s water supply and wildlife, the Pennsylvania Department of Environmental Protection (DEP) established a Water Quality Standards program as required by the federal Clean Water Act. All Commonwealth waters are protected for a designated aquatic life use as well as a number of water supply and recreational uses as listed below:
EV (Exceptional Value Waters) — waters that constitute an outstanding national, state, regional or local resource, such as waters of national, state or county parks or forests, or waters that are used as a source of unfiltered potable water supply, or waters that have been characterized by the Fish Commission as “Wilderness Trout Streams,” and other waters of substantial recreational or ecological significance.
HQ (High Quality Waters) — a stream or watershed with exceptional quality waters and environmental features that require special protection.
CWF (Cold Water Fishes) — maintenance and/or propagation of fish species and flora and fauna that are native to cold water habitats.
TSF (Trout Stocking) — maintenance of stocked trout from February 15 to July 31 and maintenance and propagation of fish species and flora and fauna which are native to warm water habitats.
MF (Migratory Fishes) — passage, maintenance and propagation of fishes which ascend to flowing waters to complete their life cycle.
WWF (Warm Water Fishes) — maintenance and propagation of fish species and flora and fauna that are native to warm water habitats.
Riparian buffers are recognized as a vital feature for protecting and reclaiming waterways. A riparian buffer is an area of vegetation that is maintained along the shore of a water body to protect stream water quality and stabilize stream channels and banks. The riparian buffer reduces the amount of runoff pollutants entering the stream. It also controls erosion, provides leaf-litter to the stream and habitat for many desirable species of amphibians, reptiles, mammals and birds. If wide enough, riparian buffers function as corridors for migrating large and small mammals. The riparian vegetation affects the stream channel shape and structure, as well as the stream’s canopy cover, shading, nutrient inputs and amount of large woody debris entering the stream. Riparian canopy cover (branches and tree crowns overhanging a stream) is important not only for its role in moderating stream temperatures through shading, but also as an indicator of conditions that control bank stability and as an energy source from leaves that will fall into the water. Aquatic macroinvertebrate organisms such as stoneflies eat, shred and break the leaves into coarse and fine particulate organic material that becomes food for other stream organisms. The Lehigh Valley Planning Commission recommended a 75 feet riparian buffer in its model Riparian and Wetland Buffers regulations.
A floodplain is the low lying area adjacent to a stream, river or watercourse that is subject to periodic flooding. Naturally vegetated areas as floodplains help to trap sediment from upland surface runoff ultimately leading to the creation of proper downstream conditions required for aquatic life. Regulation of floodplains helps to protect open space and habitat areas, preserve and enhance water quality and quantity, and prevent loss of life, health hazards, and property damage. These areas also store large amounts of water, which can be a source of aquifer recharge. Many of the most scenic areas in Lehigh and Northampton counties are found within the floodplains of the Lehigh and Delaware rivers and many of the larger streams.
For regulatory purposes, a floodplain is defined by the 100-year flood. The Federal Emergency Management Agency (FEMA) identifies the 100-year flood as the flood elevation that has a one percent chance of being equaled or exceeded each year. Thus, the 100-year flood could occur more than once in any given period of time. The 100-year flood, which is the standard used by most federal and state agencies, is used by the National Flood Insurance Program (NFIP) as the standard for floodplain management. The Pennsylvania Floodplain Management Act (Act 166 of 1978) requires municipalities identified as being flood-prone to enact floodplain regulations which, at a minimum, meet the requirements of the NFIP.
Wetlands + Hydric Soils
Wetlands are areas that are inundated by surface or ground water at a frequency and duration sufficient to support vegetation typically found in saturated soil conditions. Wetlands include swamps, marshes, fens and bogs. Many of these areas are considered seasonal wetlands, in that they are dry during one or more seasons every year. The quantity of water present and the timing of its presence determine the functions of a wetland. Even wetlands that appear dry for significant portions of the year, e.g., vernal pools, can provide significant habitat for a variety of species.
Wetlands are one of the most biologically diverse systems in the world and perform a variety of important physical and biological functions. Wetlands have important filtering capabilities for collecting runoff before it reaches rivers and streams, maintain stream flow during periods of drought, and can assist in groundwater replenishment. Additionally, wetlands are ideal locations for environmental education opportunities and scenic viewsheds.
Lehigh and Northampton counties contain over 1,000 individual sites that can be classified as wetlands. Wetlands and their associated hydric soils are found in every municipality; however, the largest concentrations occur in Upper Mt. Bethel Township and along the base of Blue Mountain in both counties. There are many problems associated with developing on or near wetlands and hydric soils, e.g. wetlands located in floodplains are often flooded, hydric soils are easily compacted, and high groundwater tables are not suitable for the installation of on-lot septic systems.
Slopes with grades of 15% to 25% are considered steep; slopes with grades greater than 25% are very steep. Steep slopes are vulnerable to damage resulting from site disruption, particularly related to soil erosion. Erosion of steep slopes can be a serious problem as all soils are subject to movement as the slope of the landscape increases. If disturbed, these areas can yield heavy sediment loads on streams and wetlands degrading water quality and disturbing aquatic habitat. Increased sedimentation also increases flood hazards by reducing the floodwater storage capacity of drainage ways. The steepest slopes in the Lehigh Valley are found along the Blue Mountain and South Mountain. A notable characteristic of steep slope areas is that they are nearly all wooded; very few steep slopes are used for cropland or pastures due to their lack of suitability for agriculture. The identification and protection of these areas can provide open space, maintain biodiversity, and protect communities from hazards related to steep slope disturbance.
In Lehigh and Northampton counties, 46 of the 62 municipalities are underlain entirely or in part by carbonate rock. These carbonate formations are located in the Lehigh Valley’s urban core. They provide the primary raw material for the local cement industry and they lie under the most fertile soils. Carbonate rock has the potential for sinkhole formations which are fairly common in the Lehigh Valley. When sinkholes occur in developed areas, they can cause severe property damage, injury and the loss of life, disruption of utilities and public services, and damage to roadways.
Woodlands are valued for many reasons. They provide recreational opportunities, such as nature study, hunting, hiking and horseback riding. Woodlands can be used for firewood harvesting, commercial timbering, and as land use buffers and boundaries between non-compatible land uses. Many species of birds and wildlife depend on large, unbroken wooded tracts for survival. Certain species, e.g. some songbirds, require interior woodlands, which are areas within forests that are not affected by the conditions that exist along the edges of the woodland. Woodlands also mitigate environmental stressors by reducing stormwater runoff, filtering groundwater recharge, controlling erosion and sedimentation, moderating local microclimates, and purifying the air. The largest concentrations are found along the mountain ranges and hillsides adjacent to major stream and river corridors. Woodlands are commonly found on other environmentally sensitive areas such as steep slopes and floodplains, adding to their significance and need for protection. Communities can mitigate the loss of the region’s woodland resources with land development and site design ordinances or policies.
Natural Heritage Inventory
The Lehigh Valley has many important natural areas worthy of protection, such as rare plants, threatened and endangered animal species, and high quality natural habitats. It is areas such as these that provide the hubs and nodes of the Lehigh Valley greenways network. The LVPC contracted with the Western Pennsylvania Conservancy (Pennsylvania Natural Heritage Program) to complete a study titled Natural Heritage Inventory of Lehigh and Northampton Counties Update 2013. This document was an update to the 2005 report (the original study was completed in 1999) and identifies the outstanding floral and faunal features in the Lehigh Valley. The project was financed in part by a Keystone Recreation, Park and Conservation Fund Program grant from the Pennsylvania Department of Conservation and Natural Resources Bureau of Recreation and Conservation and Pennsylvania Department of Transportation.
The completed 2013 update report for the Lehigh Valley can be found on the Pennsylvania Natural Heritage Program's County Natural Heritage Inventories Page.
Natural Resources Plan
Natural resources in the Lehigh Valley are made up of rivers and streams, wetlands, floodplains, natural heritage areas, mountains and woodlands. Interconnected natural resources provide numerous benefits. They provide habitat and maintain biodiversity; protect and enhance water quality; provide aesthetically pleasing areas to experience; filter pollutants from water, soil and air; recharge groundwater aquifers; provide recreation opportunities; and buffer developed areas from flooding ultimately saving lives, money and property. Voters have spoken very clearly in public opinion surveys conducted over the past 30 years that they want to preserve these important natural resources.
The Natural Resources Plan of the Comprehensive Plan The Lehigh Valley … 2030 identifies and evaluates the important natural resources in the Lehigh Valley and what should be done to preserve them. This information is based on data created by the Lehigh Valley Planning Commission (LVPC), Pennsylvania Science Office of The Nature Conservancy (TNC), Pennsylvania Department of Environmental Protection (DEP) and others.