Plum Run and its Watershed
A Tutorial in Stream Ecology Using Google Earth

The purpose of this tutorial is to provide information about stream ecology, and in particular the ecology of Plum Run in Chester County, southeastern PA. Thoroughly investigating the data as suggested in the instructions below should require 90-120 minutes. The tutorial requires the use of Google Earth, and the latest version should first be downloaded from


This tutorial was created byChristopher Robinson, with assistance from West Chester University faculty members Winfield Fairchild (Department of Biology), Timothy Lutz (Department of Geology and Astronomy), Gary Coutu and Brian Ochieng (Department of Geography and Planning). Graduate students Danielle Difederico and MikeMcGeehin, and undergraduates Katherine Broadbent and Danielle Varnes performed much of the fieldwork, laboratory analyses, and assembly of GIS information. We thank the Pennsylvania Department of Environmental Protection for analysis of total phosphorus samples, and Jane Fava and Kathy Campbell of the Brandywine Valley Association for logistical support. We also thank SeaGrant Pennsylvania.

Stream Network with Numbered Samply Sites

Fig. 1 (above): Stream network, with numbered sampling sites, and land use within the Plum Run watershed. The background is a satellite image of the area.


Getting Acquainted with Google Earth

Begin by downloading the Plum Run Google Earth tutorial file (kmz file) to your computer. Then double-click on the file to open it; wait patiently until Google Earth has fully loaded all of the files, and has zoomed in on southeastern Pennsylvania. A “sidebar” should become visible on the left side, with a list of themes or "chapters" that you will use to investigate the ecology of Plum Run and evaluate options for restoring the stream. You can make the sidebar narrower or wider by dragging the vertical divider separating it from the map either left or right.

To start a chapter in the lefthand sidebar, check its layer (for example ), then double click the blue folder icon next the chapter name to open it (). Google Earth will then zoom in on the layer. Each chapter has sublayers, connected by a vertical line to the right of the chapters in the sidebar (and some sublayers may have their own nested sublayers even further to the right in the sidebar). To view a sublayer within a theme, click the "+" mark next to it (changing it to a “-“) to expand it. To close a chapter click the check mark in the check box (leaving it blank), click on a small square in the checkbox to turn off all contained views, and then collapse the layer by clicking the "-" next to it (changing it back to a “+”). Collapsing all unused chapters is important to save space on the sidebar panel.

First make sure that the section Search, located at the top of the sidebar, is closed by clicking the triangle symbol (so that the downward-pointing triangle now points to the right). Now set the elevation value: Go to Tools\Options\3D View and, in the Terrain Quality section, type 3 for the elevation exaggeration value. Then click OK. Setting the value to 3 displays the terrain so that differences in surface topography are slightly exaggerated and more discernible.

You can view the Plum Run watershed in a variety of ways using the navigation tool (seen here at left) located on the upper righthand side of the Google Earth map. Click the "+" symbol on the vertical bar to zoom in, or “-“ symbol to zoom back out (careful! one click at a time or you’ll be out in space). Click on the same symbols on the horizontal bar to tilt the view. Holding the left mouse button down while clicking the "N"orth symbol and then moving the mouse changes the heading (orientation) of the view. Finally, the map can be repositioned by clicking and dragging with cursor (“hand” icon). Try out each of these tools before proceeding.


It’s time to begin. Expand the Introduction (by changing the “+” to a “-“). First examine the larger Brandywine Creek network and its watershed by clicking the checkbox for the Brandywine Creek and double clicking on its folder to zoom in on this sublayer. The Brandywine, located primarily in Chester County, Pennsylvania, is one of several large water sources that empty into the Delaware River. Click on the checkbox for Brandywine tributaries to see the network of streams that feed the Brandywine, then check the box for Brandywine Watershed to see the slightly darkened “drainage basin” from which it gets its water. Some of these tributary streams are in better ecological condition than others. Place a check in the box for Red Streams (Impaired) and also expand it (change its “+” to a “-“) in order to see the names and locations of 9 impaired streams. Plum Run, located in the southern part of the Brandywine watershed (find it by checking its checkbox off and on again), drains into the Brandywine River near Lenape Picnic Park. Plum Run is currently considered impaired (because of high levels of bank erosion and sediment export, poor water quality and its depauperate invertebrate community), based on a survey near its mouth in 1997 by personnel from the PA Department of Environmental Protection. The Brandywine Valley Association, or BVA (find it in the sidebar near the top of the chapter list of sublayers, and click on its checkbox to find its location on the map) is a principal environmental organization attempting to return some of these red (impaired) streams to blue once more. Does the BVA lie within the Brandywine Creek Watershed? ____ What is its location relative to Plum Run? ____________ Clicking once on its icon brings up a pop-up sign pointing to the Christmas tree icon; clicking on the name in the pop-up brings you to the BVA website and further information on its activities.


Remove the small square in the checkbox for Introduction, then collapse it. Now expand the Bearings chapter. Among its sublayers, first click the checkbox for Plum Run and double click on its folder to see the stream network. Then show the Brandywine Creek into which it flows. Now click on the checkbox for West Chester University (its sublayer has a “tentlike icon). Use the navigation tool at the upper right to a) orient it facing north, b) change the tilt so you can look down on it more directly from above, and c) enlarge it. Approximately where on North Campus is the “tent” symbol positioned? _____________________________________ (hint: You should be able to locate the Schmucker Science Center, which had a small parking lot behind it when this photo was taken in 2000; the new Boucher Building has since taken up much of this space). Notice that a part of Plum Run, shown in lighter blue, actually passes beneath the university as a stormwater sewer pipe. What buildings on North Campus are nearest to this underground portion of Plum Run? ____________________________________________________

There are two main "branches" to Plum Run. The "East Branch" first surfaces just behind the High Street Texaco station on the west side of High Street opposite the new Performing Arts Center. To find this source click the checkbox for the sublayer East Branch Origin and double click on its icon in the map to zoom in on the location and see a picture of the stream where it first emerges from a storm sewer pipe. How wide does the East Branch appear to be at this point? ________ Close the photo. Can you locate High Street just east of the picture? Double click on either the Plum Run sublayer or the Plum Run Watershed sublayer to zoom out and get reoriented, then find the West Branch Origin (bearing the name "Plum Run" on most maps of the area) and note that it begins next to a university parking lot just west of New Street. Based on the photo, what kind of material dominates the streambank next to the parking lot? __________________ The East Branch and West Branch join just north of the Strodes Mill Art Gallery near the junction of Rte 52 and Tigue Road. (To see a picture of the art gallery check its box and double click the camera icon for Convergence of West and East Branches). The stream then passes southward through the Radley Run Country Club Golf Course and empties into the Brandywine Creek near the Lenape Picnic Park. Check the boxes for the Lenape Picnic Park and Radley Run Golf Course sublayers to see additional features of importance in later chapters and further get your bearings.


Elevational Gradients

Close Bearings, open the Topography chapter, and turn on the Plum Run, 5ft Contour and Stream Stations sublayers. Zoom in on a central portion of the watershed. Each of the black curving lines consists of a series of locations with identical elevation (zoom in on a portion of the watershed if necessary to see this more clearly). Each adjacent "isoline" represents a difference in elevation of 5 feet. Are locations where the lines are closer together steeper or do they have gentler slopes? ________________

Navigate to site 5, on a small tributary stream entering the main stem of Plum Run from the west just upstream of the golf course. Work your way upstream on the tributary (not Plum Run itself) using the hand tool to shift the image, continuing upstream. Notice that the contour lines tend to form "V"s as they cross the stream. Does the tip (bottom) of the "V" point upstream or downstream in the tributary? ___________ What does this tell you about how the stream has modified the elevation of the land immediately surrounding it?  ________________________________________________________

To get a better sense of elevational gradient within the watershed, and a better sense of how the stream has carved out its valley from the surrounding land, turn on the sublayer Elevation Relief Overlay and double click to zoom out.  What colors in the overlay denote the highest ground? ______________________________ What color indicates the lowest portions of the watershed? ___________________ It may not surprise you that water flows downhill!   When done, collapse the Stream Station sublayer.

"Stream gradient" refers to the amount of altitudinal change per unit of stream distance.  Headwater stream segments with steeper gradients tend to have a) more “riffle” habitat, b) higher water velocities, and c) substrates dominated by larger particles (e.g., gravel).  Low-gradient downstream segments usually have more quiet water and substrates consisting of small particles (e.g., silt).  Most stream invertebrates are more abundant in riffles, where there are rocks to cling to, fast water to bring oxygen and food particles, and shallow water reducing the likelihood of being eaten by large fish.

Click on the icon for site 4, a tributary of the East Branch (sites 4 and 9 are very close together, but will separate out when you first try to click on them; click on the very top of the clipboard icon for site 4 to obtain a picture and accompanying graphs).  The researcher in the photo is Danielle Difederico, who completed her thesis on the fish and invertebrate communities of Plum Run. In the graph at the upper right, notice that the gradient is relatively steep in this portion of the stream network (approximately how many meters does stream drop in the 30 m section mapped? _________ The calculated gradient (= [change in vertical elevation]/[horizontal distance]) is 5%.  Also note the absence of deep pools at this site (water level is shown as a blue line, whereas the elevation of the streambed is a black line).  Most of this stream segment consists of riffle habitat, just a few cm in depth.  

For contrast, click on site 6, a downstream site.  Notice that, over a 50-m stretch of stream, the elevation of the water surface (blue line) hardly changed at all; the stream simply became deeper. Based on the picture and graph, is the site dominated by riffles or pools?


Stream geomorphology can be altered by human activities. Click on site 8, where the main stem passes through the Radley Run Country Club, and examine both the photo and graph at the upper right.  How has the Country Club stabilized the stream banks? ___________________.  Small “waterfalls”, added at intervals to help aerate the water, can also be seen in both the picture and graph.  


Turn on the Bedrock sublayer.  Elevational gradients often reflect differences in the rates of weathering of the underlying bedrock (more easily weathered rock tends to be lower in elevation). The bedrock beneath the Plum Run watershed consists largely of four rock types, color coded in the sidebar on the right. Based on their positions and relative elevations in the watershed, which of the four rock types is probably most easily weathered?  _____________________________________________________


Close the display and minimize Topography, expand the Geomorphology chapter, and click the checkbox for Plum Run Watershed.  The term "geomorphology" is a composite description of stream size, shape, water flow and other physical characteristics. Stream geomorphology is (surprise!) strongly influenced by topographic features of the watershed.

Stream Order

The calculation of "Stream Order" provides an indication of stream size and “discharge” (the amount of water passing a given point per unit time). A first order stream segment is defined as having no tributaries. A second order stream has at least 2 first-order tributaries. A third order stream has at least 2 second-order tributaries, etc. Click the checkboxes for Stream Orders 1-4 in sequence to see their location in the watershed.  What is the stream order of Plum Run where it reaches the Brandywine Creek? _______________

Click the checkbox for Stream Stations.  Fourteen sites along the creek, now indicated by flags, were sampled during summer 2005.  Turn on the Data Table layer to show a small portion of the data collected for each site. Look for the stream order column at the right end of the table. Based on the data table, how many sites were first order stream segments? _______


Stream discharge is highly variable, both in space (downstream locations experience greater discharge as a result of the greater accumulation of water from upstream) and over time (water supply varies predictably with season, and less predictably immediately following precipitation events.)  

The discharge information provided for Plum Run was obtained during mid-summer under "base flow" conditions (unaffected by rain).  Where does the water in the creek come from if it hasn’t rained recently? ________________________________ Does the East Branch or West Branch appear to carry more water to their confluence?  (Compare the discharge at site 14 on the East Branch vs. site 11 on the West Branch.) __________________________________________________________________.

The much higher discharge immediately after rain events largely results from overland runoff into the creek. Note, for example, the occurrence of three small floods on the Brandywine Creek just downstream of Plum Run during one winter holiday break in Figure 2.  What was the base flow, in cubic feet per second (cfs) just prior to the biggest of the three rain events? _______cfs  What was the peak discharge? _____cfs   Based on Figure 3, what is the relationship between stream order and baseflow discharge?  __________________________ Current daily discharge data can be obtained at the U.S.G.S.  National Water Information web site

Hydrography of Brandywine Creek

Fig. 2. (above) Hydrograph of the Brandywine Creek at Chadds Ford, PA (courtesy of the United States Geological Survey).


Relationship between stream order and discharge at 14 sites

Fig 3 (above) Relationship between stream order and discharge at 14 sites.


Riparian Vegetation

Close Geomorphology (first clicking off the small square to remove displays of its sublayers) and open the chapter on Riparian Vegetation.  Streamside (riparian) vegetation influences the stream biota in several ways. First, riparian forest canopies help shade the stream, particularly at lower order sites where stream branches may extend over the entire stream channel. Shading reduces stream water temperature, thereby increasing the capacity of the water to hold oxygen. In contrast, stream segments surrounded by meadow grasses or mowed lawns are typically warmer. These “meadow” streams are also narrower and more deeply "entrenched" (forming a deeply cut "U" in cross section), as shallow rooted grasses do little to prevent the erosion of deeper soil layers. Whereas riparian forests provide nutrition to a stream in the form of fallen leaves and woody debris, meadow streams typically have higher rates of photosynthesis by algae within the stream, owing the greater availability of light to sustain photosynthesis (riparian forests are considered better for stream health!).

Display the sampling sites sublayer (sites should now appear as clipboards). Find Site 5 and then click on the upper end of its clipboard icon to display a photograph of the stream segment with its riparian vegetation. What kind of vegetation borders the stream? _____________________  Note how steep the banks are (a cross sectional profile that crosses the stream in two places is shown in the graph at the lower right). Sites 1, 10 and 11 have similar vegetation and cross-sectional profiles

Now find site 9 on the East Branch and click on its icon to view a picture and cross-sectional profile of the site. What is the surrounding vegetation? __________________Is the degree of entrenchment (narrowness of the stream and steepness of the banks) greater than or less than that at site 5? _________________ Site 13 is similar to site 9 in its cross-sectional profile.


The Stream Biota

Close Riparian Vegetation, open the Stream Biota chapter, and check the box to view Plum Run. This chapter examines the distribution of invertebrates and fish within the stream, and their relation to water quality and stream size.

Stream Invertebrates

The stream invertebrate community includes crustaceans such as crayfish and amphipods, snails and a wide variety of aquatic insects.  Stream invertebrates respond to both geomorphology and water chemistry.  The numbers and kinds of species present can thus provide a valuable indication of habitat impairment at a site.  For example, aquatic insects such as stonefly larvae (shown in Figure 4a) require cool water with abundant oxygen, and are likely to be found only in smaller (e.g., first order) stream segments surrounded by trees that shade the stream and maintain cool water temperatures.  By contrast, most net-spinning caddisfly larvae (Figure 4b) are more tolerant of warmer water and are more typical of downstream sites.  

Click on the Sampling Sites Data sublayer at the bottom of the chapter list.  At what site is the stonefly family Leuctridae (LEU) most abundant? _____ What is its stream order and riparian vegetation? (view a photo of the site if necessary) ____________________________________________  At what two sites are larvae of the caddisfly family Hydropsychidae (HYD) most abundant? _______ Are these sites on the East Branch, West Branch or downstream on the mainstem? ___________________________  

Pictures of larva

Fig. 4a-b. Pictures of a stonefly larva on the left ( and a net-spinning caddisfly larva on the right (

One commonly used way to infer water quality at a site based on the invertebrates present is the Family Biotic Index (FBI), based on 10 measurements of water quality.  High FBI values indicate a preponderance of very tolerant invertebrates, and thus indicate impaired water quality, whereas lower numbers provide evidence of progressively better water quality.  Which site had the best water quality based on its FBI score? _______ Which had the worst water quality? ______  Turn off the Sampling Sites Data sublayer and click on the sublayer Sites – FBI values to see more general patterns of water quality based on the FBI; you will need to zoom in on the East Branch to see the only site location with excellent water quality.  

Another invertebrate-based metric of water quality, the MAIS index, is calculated very differently from the FBI; high values for the MAIS index indicate a healthy invertebrate community, while low values indicate impairment.  Based on Figure 5, which two sites appear to be most impaired? _________ Where are they located in the watershed? ___________________What is the relationship of the MAIS score to specific conductance (dissolved ions) in the water?  ____________________________________

Graphic of Relationship between conductance and MAIS

Fig. 5 (above).  Relationship between specific conductance and MAIS score at 14 sites (numbered in the figure).


Fish communities are often organized primarily by stream size.  Downstream (higher-order) stream segments typically have more kinds of fish and larger fish (many of them potential predators on smaller species).  For example, most species of bass and sunfish are confined to larger pools near the mouth of Plum Run.

Fig.6a-b (above).  Pictures of  (a) Rock Bass and (b) Blacknose Dace.

To observe the distribution of Rock bass (Fig. 6a) within the stream network, close Sites – FBI values, click the check box for Rock bass, and look for images of fish at the sampling sites. How far up into the East Branch and West Branch does its distribution extend?   ________________________________________________

By contrast, many smaller minnow species (family Cyprinidae) such as Blacknose dace (Fig. 6b) are better adapted to small streams. They may be rare or absent, however, from locations with larger, predatory fish. View the distribution map for the Black Nose Dace by clicking its check box.  At which two downstream sites with abundant Rock bass are Blacknose dace NOT present? (Click both sublayers on and off if necessary to see the distributions of the two species.)


Examine Figure 7 below showing the effect of distance from Brandywine Creek on total fish species richness. What effect does distance upstream have on the total number of fish species? _____________What changes in stream habitat may have eliminated some species from upstream sites? ________________________________

Effects of Distance on Species Richness

Fig. 7.  (above) Effects of distance from the confluence with Brandywine Creek on the number of fish species at 14 sites in Plum Run.


Land Use

Close Stream Biota, open the Land Use chapter and begin by clicking on the sublayers “Plum Run” and “Plum Run Watershed” near the bottom of the chapter list. The intent of this chapter is to make you aware of current problems related to land use within the Plum Run watershed.

Land Use Patterns

Some land uses (e.g., “parking”, “transportation”, “commercial”) typically have an abundance of impervious surfaces (e.g., roads and driveways, rooftops) and thus experience considerable stormwater runoff; the runoff may also be contaminated by road salts and other materials.  Agricultural and residential land typically provide intermediate levels of overland runoff to streams, and may also add fertilizers and herbicides or pesticides to the runoff.  By contrast, forested land (the watershed was almost entirely forested before its alteration by humans) has much more capacity to retain rainfall and provide infiltration of precipitation to the groundwater.  

Figure 8 below summarizes the relative aerial proportions of the major land use types in the Plum Run watershed.  What percentage of the watershed consists of single family (SF) or multi-family (MF) residential land? _____________  What percent remains as forest? ___________

Percentages of Selected Land Uses with the Watershed

Fig. 8. Percentage composition of major land use categories within the  Plum Run watershed.

The close proximity of particular land uses to the stream itself may accentuate their effects.   Click on the sublayer Land Use Type to see the locations of particular land uses relative to portions of the stream. Is the East Branch or West Branch better protected by forest?


What particularly large tract of land surrounding the lower main stem of Plum Run is classified as “recreation”? (turn off the Land Use sublayer to see the underlying aerial photo if necessary)


Municipal Jurisdictions

Watersheds inevitably cross political boundaries, often making stream conservation and restoration difficult because of the need for coordination among multiple governmental entities.  Turn on the Municipalities layer. How many municipalities have jurisdiction over portions of the Plum Run watershed?  Municipalities are outlined with color-coded boundaries.  If you’re uncertain about their locations double-click on a municipality to zoom in on it.  Which municipality is probably most concerned about water quality in the headwaters? _______________ Flooding events near the Strodes Mill Art Gallery on the upper main stem has become a concern for which municipality? ____________________________________________

Stream Restoration

Close the Land Use Chapter and open the final (!) chapter on Stream Restoration, which should help you determine how and in what portions of the watershed stream restoration can best be accomplished.  Two kinds of restoration are emphasized: flood control and the reestablishment of forested riparian buffers.  

Flooding, Floodplains and Wetlands

Turn off Land Use Types and activate the Floodplain sublayer.  During flood events, water spreads out over a portion of the stream's floodplain. Floodplains delineated as blue areas surrounding the stream indicate land which would be impacted by a 100-yr flood (likely to occur at an average frequency of 100 years; somehow major floods seem to happen more often than predicted if you're a streamside landowner!). These lands are typically restricted to development and also have natural plant communities which are adapted to periodic flooding. Note how surprisingly wide the floodplain is near the origins of both the East Branch and West Branch, despite the small size of these streams at base flow.  What land use(s) near the headwaters may have contributed to this problem? ______________________________________________________________

Wetlands often help protect stream water quality by providing low-lying areas where floodwaters (see Restoration below) are stored and infiltrated to the groundwater, and also by intercepting materials before they enter the stream.  Wetlands are protected from development by federal and state legislation.  Click on Wetlands (near the top of the chapter list), showing information compiled by The National Wetlands Inventory.  Do the wetlands primarily occur in the floodplain near the stream, or on higher ground at more distant locations within the watershed? _______________ Predict what would happen to the stream if the floodplain and its wetlands were converted to other land uses. _____________________________________________________________________

Stormwater Management

West Chester University maintains several stormwater management basins (SWM) designed to limit peak flows, and to reduce the downstream transport of sediments, in the East Branch. Double click on Stormwater Management sublayer.  On the upper East Branch, click the “egret”  symbol Small image of Egret to view a photo of the new stormwater management basin adjacent to the Performing Arts Center, labeled "Performing Arts Center SWM".  The new retention basin is intended to reduce flooding that might otherwise result from the extensive stormwater runoff associated with parking lots and buildings in this portion of the university.  

Also view the much older retention basin directly south of the Sykes Student Center, labeled "Student Center SWM”.  Trees have overgrown the Sykes basin, now largely filled in and less effective in controlling flooding as a result.  Which portion(s) of Plum Run are likely to be most affected by these two retention basins? _________________________________________________________________

A much more elaborate retention facility, consisting of two retention ponds and a a "polisher" established in sequence to control runoff from new student housing on the university's South Campus, is shown by clicking on the egret icon labeled "South Campus SWM". The polisher itself, at the lower right (downstream end) of the composite photo, is intended to allow further sediment retention before the water reaches Plum Run, and to spread water over a wide area to allow increased infiltration to the groundwater.  Does this facility protect the East Branch or West Branch? ___________ Close  

The Riparian Corridor

Close the Wetlands and Floodplain and active the Land Use – Corridor sublayer, indicating land use within a 100 ft corridor directly adjacent to Plum Run.  This corridor  is particularly critical to the health of the stream, and is a logical place to start in terms of restoring stream water quality.  You can see which land uses currently occupy this corridor by expanding and viewing its nested sublayers one at a time.  Which land uses are most typical of the corridor? ___________________________________________.  Look for opportunities to change existing land uses within the corridor into land uses more likely to improve water quality and reduce flooding within Plum Run.

Thank you for taking the time to complete this tutorial.  Questions about the tutorial approach developed here can be directed to Dr. G. Winfield Fairchild, Department of Biology, West Chester University, West Chester, PA 19383 (