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Mill Creek (MC-01, MC-02, MC-03, and MC-04)

About the site:

There are four stations located in the study area on Mill Creek . Sampled since 2010, MC-01 is located at the downstream end of the watershed north of College Parkway while sites MC-02, MC-03, and MC-04 are found in the headwaters to the south of College Parkway. Impervious surface levels range from 17% at MC-04 to 23% at MC-01, but an extensive forested riparian area buffer (~70 to 150 feet, depending on watershed location) exists along this stream between the upstream and downstream sites. No restoration has occurred along these sample reaches, but restoration activities are planned to occur within the next 1 to 2 years.

CY-01

CY-01

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2018 Summary Report:

Site MC-01
Time FrameBIBI (Condition)FIBI (Condition)RBP (Condition)
2018 Results2.71 (Poor)2.33 (Poor)125 (Partially Supporting)
Cumulative Average (2010-2018)2.59 (Poor)2.67 (Poor)121 (Partially Supporting)
3-year Running Average2.62 (Poor)2.50 (Poor)121 (Partially Supporting)
Site MC-02
Time FrameBIBI (Condition)FIBI (Condition)RBP (Condition)
2018 Results1.00 (Very Poor)1.67 (Very Poor)123 (Partially Supporting)
Cumulative Average (2010-2018)2.46 (Poor)1.67 (Very Poor)110 (Partially Supporting)
3-year Running Average1.86 (Very Poor)1.67 (Very Poor)118 (Partially Supporting)
Site MC-03
Time FrameBIBI (Condition)FIBI (Condition)RBP (Condition)
2018 Results1.00 (Very Poor)1.67 (Very Poor)136 (Supporting)
Cumulative Average (2010-2018)2.52 (Poor)2.00 (Poor)118 (Partially Supporting)
3-year Running Average2.14 (Poor)1.84 (Very Poor)124 (Partially Supporting)
Site MC-04
Time FrameBIBI (Condition)FIBI (Condition)RBP (Condition)
2018 Results3.00 (Fair)1.67 (Very Poor)121 (Partially Supporting)
Cumulative Average (2010-2018)2.46 (Poor)1.89 (Very Poor)110 (Partially Supporting)
3-year Running Average2.81 (Poor)1.84 (Very Poor)110 (Partially Supporting)

Benthic IBI: 

Site MC-01: Located furthest downstream of all the Mill Creek sites, MC-01 had a BIBI score of 2.71 (Poor) in 2018, an increase from 2017, where it received a 2.43.However, this score is in line with the three-year running average of 2.62 and greater than the cumulative average of 2.59. For 2018, chironomids dominated the sample, with lesser numbers of oligochaetes and riffle beetles present. Springtails and snails were also common at this site in 2018.

MC-01 Sample of Insects Collected by Sample Year

CY01 Bugs
Click to enlarge

Site MC-02This site is located upstream of MC-01 and downstream of the confluence of the two reaches that contain MC-03 and -04. This site is surrounded by a well-forested riparian area. In 2018, this site received a BIBI score of 1.00, or Very Poor. This outcome was due to less than 60 total bugs collected in the sample and is the lowest score was automatically given. The 2018 sample was dominated by chironomids with predaceous diving beetles, caddisflies, snails, and craneflies, among others observed. The cumulative average and three-year running average of 2018 was 2.46 (poor) and 1.86 (Very Poor), respectively.

MC-02 Sample of Insects Collected by Sample Year

CY01 Bugs
Click to enlarge

Site MC-03: Moving upstream from MC-02, MC-03 is located on a tributary on the upstream right side of the confluence with the MC-04 tributary. It is similar in character to the other Mill Creek sites described previously in that it is surrounded by a forested riparian area. 

The 2018 BIBI was 1.00 (Very Poor). Like MC-02, this score was due to less than 60 total bugs collected in the sample and is the lowest score was automatically given.   Chironomids dominated the sample, with lesser amounts of, oligochaetes, and caddisflies present, a trend in occurrence that has been fairly consistent year over year. The cumulative and three-year running average for this site are 2.52 (Poor) and 2.14 (Poor), respectively.

MC-03 Sample of Insects Collected by Sample Year

CY01 Bugs
Click to enlarge

Site MC-04: MC-04 is located upstream from MC-02 and is on a tributary on the upstream left side of its confluence with the MC-03 tributary. It is similar in character to the other Mill Creek sites described previously.  

The 2018 BIBI for this site was in the Fair range, with a score of 3.00. This was a big increase from past years of several scores in the Poor category. As in prior years, the sample was dominated by chironomids, with lesser amounts of oligochaetes andcaddisfliesIncreases in scraper taxa and in percent climbers drove the BIBI increase. The cumulative and three-year running averages for this site are 2.46 (Poor) and 2.81 (Poor), respectively.

MC-04 Sample of Insects Collected by Sample Year

CY01 Bugs
Click to enlarge

Fish IBI:

Site MC-01The FIBI was scored as Poor (2.33), a slight decrease from its score or 2.67 in 2016. A total of eight species were observed in 2018: American eel, bluegill, pumpkinseed, brown bullhead, golden shiner, spottail shiner (Notropis hudsonius), largemouth bass, and banded killifish (Fundulus diaphanous). With the high level of imperviousness in the upstream drainage area (26%), the number of species found here in 2018 was unexpected, but synonymous was recent years.

Site MC-02The FIBI score in 2018 was in the Very Poor range, at 1.67. A single species, American eel, was collected during the 2018 sampling. This site received the same FIBI score in 2016 with the same species found. 

Site MC-03The FIBI at this site scored in the Very Poor range (1.67). Four fish of one species, American eel, was found at this site in 2018. This is a slight decrease from past years, as the cumulative and three-year running averages are 2.00 (Poor) and 1.84 (Very Poor), respectively. 

Site MC-04The FIBI at this site was 1.67 in 2018. Two species were identified: American eel and eastern mudminnow. Total fish counts were the same from 2016 (seven). Unlike the BIBI, the FIBI indicates that poor ecological health conditions exist at this location.

Physical Habitat: 

Site MC-01Habitat conditions are what would be expected with the observed biological conditions. The RBP score was 125, or Partially Supporting. This represents a slight increase over both the cumulative average (121, Partially Supporting) and the 3-year average (121, Partially Supporting). High rates of bank erosion, sediment deposition and somewhat low levels of vegetative bank protection were all factors depressing the score here.

An examination of the cross section measurements indicates that this stream reach has experienced instability over the sampling period (2010-2018). Severe incision has occurred over the last seven years. The thalweg elevation decreased by approximately 2.75 feet between the 2010 measurement and the 2018 measurement. Major incising also occurred between 2017 and 2018, with a 1.5 foot thalweg decrease.It is likely that the bank erosion observed during the habitat assessment will be exacerbated by this elevation change in the channel bottom. Incision typically increases the frequency with which erosive high flow conditions are unable to access a surrounding floodplain, causing additional erosion (Julian and Torres 2006), although the pace and subsequent evolution of the channel can be quite variable (Beechie et al. 2008, Rosgen 1996). This reach classifies as a Rosgen G5c.

MC-01 Cross Section Comparison 

Cross Section
Click to enlarge

Site MC-02Habitat conditions show signs of improvement at this sample reach, was a 2018 score of 123, Partially Supporting. This is an improvement from the 2017 score of 109 (Partially Supporting). The 2018 score is also higher than the cumulative average (110, Partially Supporting) and the three-year running average (118, Partially Supporting).  Scores for epifaunal substrate, pool variability, and riparian area width boosted the overall index score. Sediment deposition was identified as a serious issue with this site, scoring in the low end of the Marginal range for this parameter.

The cross section at this site has shown a steady building of a right bank (downstream) depositional feature coupled with an apparent undercut observed on the left bank. If watershed conditions have initiated a reach wide adjustment in the stream’s planform, it might explain the observed sediment deposition issue identified during the RBP assessment. This reach classifies as a Rosgen B5c, although the entrenchment ratio and width/depth ratio both had to be adjusted per the methodology (Rosgen 1996) to perform the classification, supporting the idea that this channel is possibly adjusting itself to some unknown change in upstream watershed conditions.

MC-02 Cross Section Comparison 

Cross Section
Click to enlarge

Site MC-03Habitat condition scores were up sharply in 2018, with this site scoring in the Supporting range at 136, compared with the Partially Supporting score (102) it received in 2017. The 2018 value was greater than both the cumulative average and the three-year running average of 188 (Partially Supporting) and 124 (Partially Supporting), respectively. Favorable increases in epifaunal substrate, pool substrate, and pool variability account for the year over year differences in habitat conditions.

The cross section at this site has shown virtually no change over the nine years of geomorphic data collection. Incision and deposition have oscillated over the years here, with typical changes from year to year of around 0.2 feet, or less. The thalweg depth in 2018 is virtually identical to that surveyed in 2010. This particular reach in Mill Creek appears somewhat stable and classifies as a Rosgen G5c stream type.

MC-03 Cross Section Comparison 

Cross Section
Click to enlarge

Site MC-04A Partially Supporting score of 121 was obtained here in 2018. This score represents some improvement of the cumulative average of 110 and an improvement over the three-year running average of 110. In particular, poor bank stability scores and high levels of sediment deposition worked to depress habitat quality in this reach.

Very little change has occurred in the cross section since measurements began in 2010. The major difference in 2018 was the apparent increase of an undercut on the right bank (downstream) that was first observed in 2016. Future surveys will provide an understanding of the potential magnitude of bank change that might be occurring at this location. Like MC-03, this reach classifies as a Rosgen G5c.

MC-04 Cross Section Comparison 

Cross Section
Click to enlarge

Historical Data Summary:

MC-01
YearBIBI (Condition)FIBI (Condition)RPB (Condition)
20101.86 (VP)---123 (PS)
20113.00 (F)---120 (PS)
20122.43 (P)---128 (S)
20132.14 (P)---125 (PS)
20143.00 (F)---111 (PS)
20153.00 (P)3.00 (F)117 (PS)
20162.71 (P)2.67 (P)125 (PS)
20172.43 (P)---114 (PS)
20182.71 (P)2.33 (P)125 (PS)
MC-02
YearBIBI (Condition)FIBI (Condition)RBP (Condition)
20103.00 (F)---130 (S)
20112.71 (P)---107 (PS)
20123.29 (F)---102 (PS)
20132.71 (P)---104 (PS)
20143.00 (F)---103 (PS)
20151.86 (VP)1.67 (VP)93 (NS)
20161.57 (VP)1.67 (VP)123 (PS)
20173.00 (F)---109 (PS)
20181.00 (VP)1.67 (VP)123 (PS)
MC-03
YearBIBI (Condition)FIBI (Condition)RPB (Condition)
20102.71 (P)---111 (PS)
20112.43 (P)---115 (PS)
20122.14 (P)---133 (S)
20133.00 (F)---113 (PS)
20143.00 (F)---117 (PS)
20153.00 (F)2.00 (P)98 (NS)
20162.71 (P)2.33 (P)133 (S)
20172.71 (P)---102 (PS)
20181.00 (VP)1.67 (VP)136 (S)
MC-04
YearBIBI (Condition)FIBI (Condition)RBP (Condition)
20102.43 (P)---113 (PS)
20112.71 (P)---110 (PS)
20122.14 (P)---122 (PS)
20132.14 (P)---100 (NS)
20142.71 (P)---108 (PS)
20151.57 (VP)2.00 (P)89 (NS)
20162.71 (P)2.00 (P)114 (PS)
20172.71 (P)---111 (PS)
20183.00 (F)1.67 (VP)121 (PS)
All Station Summary
 Average BIBI (SD)3-Year Average BIBI (SD)Average RPB (SD)3-Year Average RBP (SD)
MC-012.59 (0.41)2.62 (0.16)121 (6)121 (6)
MC-022.46 (0.79)1.86 (1.03)110 (12)118 (8)
MC-032.52 (0.64)2.14 (0.99)118 (14)124 (19)
MC-042.46 (0.44)2.81 (0.17)110 (10)115 (5)

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