Dividing Creek (DC-01 and DC-02)

a) Fish data were collected 2015, 2016, 2018, 2020, 2022, and 2024.. 

a) Fish data were collected 2015, 2016, 2018, 2020, 2022, and 2024. 

Site DC-01: The site is located on Anne Arundel Community College property, just upstream of the College Parkway road crossing. The site’s 2024 BIBI score was 2.71 (Poor).  BIBI scores at this site have been categorized as “Poor” or “Very Poor” every year since sampling began in 2010.  The 2023 sample was dominated by flies, which comprised nearly 60% of all organisms found. Caddisflies were present in the sample for the fifth consecutive year.
 

DC-01 Summary of Insects Collected by Sample Year:

Site DC-02: This site is also located on Anne Arundel Community College property, upstream of DC-01 and just downstream of West Campus Drive.  While technically within the footprint of the restoration project completed in 2016, the sampling reach was unaltered by construction activity, therefore sampling persisted throughout the construction period. The sampling reach is situated between two areas where the stream channel was reconfigured into a series of riprap steps and large pools typical of a wetland seepage system. While not purposely converted into a pool area, the sampling site has experienced an increase in water depth, and velocity has slowed due to the impacts of the downstream pool area. At its upstream end, the sampling reach includes a constructed stone weir (a dam that raises water level) that created a pool just upstream of the site.

This site received a BIBI score of 2.14 (Poor) in 2024. The site has been in the “Poor” or “Very Poor” categories for 12 of the 14 years it has been sampled (it received a “Fair” rating in 2010 and 2015).  The 2024 sample was dominated by flies, which accounted for approximately 75 percent of all organisms. Dobsonflies were present in the sample for the first time since monitoring began, and caddisflies were present in the sample for the first time since 2021.

While the sample reach itself was not included in the construction activities, stream reaches above and below the sampling reach were dramatically altered by the restoration project. The impact that a particular stream restoration project has on reaches downstream of the restoration is not well understood. However, it is possible that the restoration work has had impacts on both sample reaches. It is also possible that an unknown water quality impairment originating upstream has caused this shift at one or both stations. The ultimate trajectory and persistence of any observed condition changes will require continued long-term sampling at these locations.

DC-02 Summary of Insects Collected by Sample Year:

Site DC-01: The site received a FIBI score of 2.67 (Poor) in 2024. Four species were observed in 2020: eastern mosquitofish (Gambusia holbrooki), American eel (Anguilla rostrata), eastern mudminnow (Umbra pygmaea), and golden shiner (Notemigonus crysoleucas).  The proportion of American eel in the sample increased for the third year in a row.

DC-01 Summary of Fish Collected by Sample Year:

Site DC-02: DC-02 received a FIBI score of  2.14 (Poor) in 2024. Four species were observed in 2024: eastern mosquitofish (Gambusia holbrooki), American eel (Anguilla rostrata), eastern mudminnow (Umbra pygmaea), and golden shiner (Notemigonus crysoleucas). 

DC-02 Summary of Fish Collected by Sample Year:

Site DC-01: In 2023, a habitat score of 120 (Supporting) was calculated for this site.  Habitat conditions have been fairly consistent since monitoring began here in 2010, earning a “Supporting” rating in all but two years.  High levels of bank stability and vegetative cover, diversity of channel flow features, and little evidence of channel alteration all contribute to the high quality habitat observed here.

Site DC-02: Habitat scores have been consistent here since 2015 and indicate some improvement since monitoring commenced here in 2010. In 2024, the sire received an RBP score of 120 (Partially Supporting).  Habitat quality at the site has remained fairly consistent, scoring as “Partially Supporting” or “Supporting” in 13 out of 15 years.

Site DC-01: A new cross section was established for this site in 2017, due to the loss of the previous years’ monuments. The establishment of a new cross section made it impractical to directly compare pre-and post-restoration geomorphology. The prior examination of the cross section (2010 - 2016) showed little alteration between 2015 and 2016. However, the site appeared to experience significant sediment inputs between the 2011 and 2012 measurements, as the thalweg elevation rose approximately 0.8 feet over that period. Elevations in-channel remained the same for 2013, but steady incision between 2013 and 2016 resulted in removal of approximately half of the in-channel sediment inputs observed in 2011 and 2012. Additionally, steady erosion of the right bank (downstream) and deposition on the left bank was noticeable between 2010 and 2016, resulting in a channel that appeared to be shifting towards the right bank while maintaining its approximate cross sectional area as it progressed. The current cross-section comparison shows little overall change between 2017 and 2023 other than slight aggradation of the stream channel.  Between 2023 and 2024, approximately 1.5 ft of bed material was scoured out along the right side of the channel. Attempts in future years to relocate the old monuments will be made when sampling, but if they are unable to be found, the 2017 established monuments will continue to be used for all future comparisons.
 

DC-01 Cross-Section Comparison:

Site DC-02: While the banks at DC-02 appear to be relatively stable, the channel bottom looks to be less so.  Between 2010 and 2021 the channel bottom incised by approximately 1.7 feet.  In 2024, sediment that had been deposited on the left side of the stream channel bottom between 2021 and 2023 was scoured out. 

DC-02 Cross-Section Comparison:

Historical Data Summary:

SD = Standard Deviation