Protection and Management Plan for the Millbrook Marsh Nature Center
The hydrology of Millbrook Marsh is dominated by surface water from two streams, Slab Cabin Run and Thompson Run, both classified as cold water fisheries that support trout. A map depicting the hydrologic regime (Map 4) has been compiled from various sources, including the Federal Emergency Management Agency’s floodplain map and direct observations. Millbrook Marsh serves a flood control function by storing surges of stormwater or meltwater from further up the watershed, arid thereby reducing peak flows and crest levels further downstream. During these flooding events, the marsh vegetation helps filter out sediments and potential contaminants contained in the stormwater, although this capacity may have been exceeded. It also functions as a groundwater discharge area for many springs.
The general hydrology of the Millbrook area is described here with a focus on streams and springs. Hydrographs generated from shallow wells at three reference wetlands are discussed in the section on Wetlands and Vegetation. Two major springs exist outside of the site, on the other side of Puddintown Road, in the Bathgate neighborhood. Bathgate Spring is on the northeast side of Orchard Road, contained in a springhouse. Another flows out of the ground at the end of Bathgate Drive, on the Bathgate Farm. These springs contribute to the marsh a continuous stream of water which enters the site along the bend in Puddintown Road. At the confluence of the two springs is an area where the water table is very high, resulting in persistent groundwater saturation. This section contains emergent and shrub wetlands located on the original Farm 12 acreage. At this time, Bathgate Spring Run is one of the healthiest of the riparian-wetland areas on the site, with little or no undercutting of the streambank, and no scouring of the stream bottom. It is the only stream on site that is not affected significantly by urban stormwater surges.
Another major spring area lies outside of the boundary of the Millbrook Marsh Nature Center, though it is part of Millbrook Marsh. A concentration of springs is found along the forested south edge of the marsh, near the west and north ends of Watkins Road and Shoferd Lane. These springs discharge through the limestone bedrock, causing the ground to be consistently saturated by water with an alkaline pH level. This important source of groundwater supports a calcareous fen, with its unique and rare community of plant species. Other springs found throughout the marsh include several along Thompson Run, and one at the east and north end of Shoferd Lane.
The water contributed to the marsh from springs varies in percentage at different times. In June of 1997, the flow leaving Millbrook Marsh at Slab Cabin Run equaled a total discharge of 21 .48 cubic feet per sec (cfs) (Fig. 3). About 7% of that came from Bathgate Spring. About 1 cfs (0.46 %) originated from smaller springs throughout the site. This changed substantially by October. After the dry summer, the total discharge was 9.67 cfs, and 21% of the water was contributed by Bathgate Spring and the other unmeasured springs. The amount of water contributed by springs was reduced to only 0.51 cfs, a 9% drop, while the reduction in stream flow was 11.3 cfs, a 40% drop (Fig. 3).
Stormwater. Wetlands associated with streams and rivers often provide a flood control function by dissipating and temporarily storing natural and stormwater flows. This stormwater, if not managed carefully however, can also cause significant damage to wetlands and riparian corridors by overwhelming the natural capability of a site. This results in a reduced flood control function. Substantial disturbance appears to have occurred in Millbrook Marsh, as evidenced by the observations of adjacent property owners and long-time residents (N. Deno, B. Niebel, pers. comm.) and by examining the stream characteristics. Surveys conducted in 1997 of reaches of Slab Cabin Run and Thompson Run within Millbrook Marsh yielded evidence that high stream flows attributable to stormwater runoff have negatively influenced the morphology of both streams. Careful consideration should be given to managing stormwater inputs into the marsh from the surrounding watershed to avoid further degradation.
In a more natural system, there would be few or no point source entries of stormwater. Instead there would be overland sheet flow and an overall, and in most cases relatively gradual, rise and fall in stream flow. This is not the situation at Millbrook Marsh where there are multiple stormwater outlets throughout the site and into the inflowing streams (Map 4). Many are located outside the bounds of the Millbrook Marsh Nature Center, but are still within Millbrook Marsh. A major input of stormwater flows into Thompson Creek before it crosses to the north side of East College Avenue. This has been a major cause of scouring and bank erosion observed in Thompson Run. One of the detrimental aspects of stream bed scouring is the lowering of the water table. Further downstream, the result is an increase in silt deposited on the stream beds of Thompson Run and Slab Cabin Run. Thompson Run also has two stormwater outlets near East College Avenue, the point at which it enters the south western corner of the Marsh (Photo 4A and 4B). The rip-rap seen in Photos 4A and 4B serves as a basking area and probable hibemaculum for snakes (K. Tamminga and 0. Roth, pers. comm.).
Two more stormwater entry points are located at the southeastern corner of Millbrook Marsh. One is located in the headwall of the B. College Ave. bridge over Slab Cabin Run near the upper parking lot of the College Township Municipal Building (Photo 5A), and one is at the lower level parking area, including runoff from the parking lot and maintenance area. This runoff flows through a swale into the floodplain (Photo 5B).
Approximately 60 m (200 ft) from B. College Ave. is another stormwater outlet flowing into Slab Cabin Run. Mother stormwater outfall is located along the boundary adjacent to the Route 322 Bypass about half way between Puddintown Road and East College Avenue. It is on the north side of the paved footpath, and drains into a short swale before dispersing in the upland vegetation.
There is evidence (high percentage of unstable banks) that high stream flows attributable to stormwater runoff have negatively influenced the morphology of Slab Cabin Run. The macroinvertebrate communities at 5 of 6 stations throughout the marsh reflected moderate degradation, which is probably due to impaired water quality associated with upstream urban and agricultural runoff. It is unlikely that the present aquatic communities in the marsh can be sustained if the volume of incoming stormwater increases or the quality of incoming stormwater declines. Adoption of best management practices for stormwater in the watershed is critical for the long term health of the marsh.
Besides the mixture of pollutants in stormwater entering Thompson Run from road runoff, there is a substantial sediment load originating from the ditch that conveys stormwater from the discharge pipes to the Duck Pond. Stabilization of this ditch would greatly benefit the aquatic communities in the marsh, and is scheduled for completion in 1998 (joint project between the State College Borough and the Pennsylvania State University).
The U.S. Environmental Protection Agency’s Rapid Bioassessment Protocol III (REP III), described later in the stream fauna section, was used to determine the condition of the macroinvertebrate community of Millbrook Marsh, and is a good indicator of aquatic health. Overall, RBP III suggests a moderate departure from good water quality for streams within Millbrook Marsh.
Photo 4A. Examples of stormwater input
into Millbrook Marsh - Road runoff from
E. College Ave. and Puddintown Road at the Thompson Run bridge, east side.
Photo 4B. Examples of stormwater input into Millbrook Marsh - Road runoff from
E. College Ave. and Puddintown Road at the Thompson Run bridge, west side.
Photo 5A. Examples of stormwater input
into Millbrook Marsh - Parking area
runoff from the College Township Municipal Building.
Photo 5A. Examples of stormwater input
into Millbrook Marsh - Culvert outfall
into Slab Cabin Run from E. College Ave. near the College Township Municipal Building.
On to Stream Fauna