Danville Dam 2018 Salvage Report: Results of the fish and freshwater mussel surveys following the removal of the

Danville Dam on the Vermilion River

Prepared by: Jeremy S. Tiemann, Alison P. Stodola, and Rachel M. Vinsel

Illinois Natural History Survey 1816 South Oak Street Champaign, IL 61877

Prepared for:

Illinois Department of Natural Resources’ Endangered Species Program One Natural Resources Way

Springfield, IL 62702

Illinois Natural History Survey Technical Report 2018(36) 3 December 2018

Executive Summary • The Danville Dam on the Vermilion River (Wabash River drainage) in the city of Danville,

Vermilion County, Illinois, was removed during the summer and autumn of 2018

• During the project, 1 fish and 905 live individuals of 23 species of freshwater mussels were relocated. These included:

o 1 Smallmouth Bass (Micropterus dolomieu) o 1 state-threatened Purple Wartyback (Cyclonaias tuberculata) o 6 state-endangered Wavyrayed Lampmussel (Lampsilis fasciola) o 1 state-endangered Rainbow (Villosa iris) o 264 Mapleleaf (Quadrula quadrula) o 217 Giant Floater (Pyganodon grandis) o 130 Fragile Papershell (Leptodea fragilis) o 91 Pink Heelsplitter (Potamilus alatus) o 86 Plain Pocketbook (Lampsilis cardium)

• One side effect of dam removal is stranding, desiccation, and predation of mussels within the former impounded areas. In addition to the live individuals, 116 fresh-dead individuals representing 18 species were observed, including

o 1 fresh-dead Purple Wartyback o 2 fresh-dead Wavyrayed Lampmussel o 1 fresh-dead Rainbow o Nearly half of these individuals (e.g., 41 Giant Floater, 7 Mapleleaf, and 3 Plain

Pocketbook) were observed during the last sampling event and were found on the gravel bar that formed at the mouth of the North Fork

• Given time, fishes and mussels should naturally recolonize the former impounded areas of the Danville Dam if habitat conditions are optimal and source populations are in close proximity

TABLE OF CONTENTS

Executive Summary .................................................................................................................... 1

Introduction ............................................................................................................................... 3

Project location .......................................................................................................................... 3

Methods .................................................................................................................................... 4

Results and discussion ............................................................................................................... 4

Acknowledgements ................................................................................................................... 6

Literature Cited .......................................................................................................................... 6

Tables

Table 1 – List of freshwater mussels recorded by date from the Danville Dam impoundment, Danville, Vermilion County, Illinois, as the dam was being removed during the summer and autumn of 2018. Data from these surveys include the number of individuals found alive (L) and those found as fresh-dead (D - likely perished as the result of being stranded as water levels receded) .................................................................................. 8

Figures

Figure 1 – The Danville Dam, prior to its removal, was located on the mainstem Vermilion River in Danville, Vermilion County, Illinois ....................................................................11

Figure 2 – Map of the Danville Dam, Danville, Vermilion County Illinois ..............................12

Figure 3 – Images from the Danville Dam removal process – which include the notching and building of a causeway into the river – throughout the project duration .......................13

Figure 4 – Trails left by freshwater mussels in the Vermilion River as the water levels receded during the removal of the Danville Dam ..........................................................14

Figure 5 – Lower end of the impounded area created by the Danville Dam on the Vermilion River ..............................................................................................................................15

Figure 6 – The state-listed freshwater mussels collected from the impounded area during the removal of the Danville Dam ...................................................................................16

Figure 7 – The old Illinois Route 1 bridge – resting directly underneath the current Illinois Route 1 / US Highway 150 bridge – was revealed after the Danville Dam was notched and its impounded waters were partially drained ..........................................................17

Figure 8 – Hydrograph of the Vermilion River (Wabash River drainage) from the USGS gage (#03339000) near Danville (located ~2 river-miles downstream of the former Danville Dam). ............................................................................................................................18

Cover photo: Dam removal sign posted at the Danville Dam construction site in Danville,

Vermilion County, Illinois, on 18 July 2018 (J.S. Tiemann photo).

INTRODUCTION Impoundments can affect river systems in a myriad of ways and have cascading effects that result in altered hydrogeomorphology and degraded habitats (Baxter 1977; Tiemann et al. 2004; Maloney et al. 2008; Csiki and Rhoads 2010; Csiki and Rhoads 2014). The resulting effects on fishes and freshwater mussels are equivocal, but include reduced native species richness and abundances or fragmented and restricted populations (Watters 1996; Dean et al. 2002; Tiemann et al. 2004; Santucci et al. 2005; Tiemann et al. 2007; Slawski et al. 2008; Hastings et al. 2016; Tiemann et al. 2016; Smith et al. 2017). Dam removal is viewed as a useful tool for restoring streams in terms of remedying altered habitats and fragmented populations (Kanehl et al. 1997; Catalano et al. 2007; Maloney et al. 2008; Burroughs et al. 2009).

The Vermilion River basin (Wabash River drainage) drains nearly 1,550 mi2 of eastern Illinois and western Indiana. The mainstem and its three largest tributaries (Salt Fork, Middle Fork, and North Fork) are relatively free-flowing except for four dams in Danville, Vermilion County, Illinois: Danville Dam (or Vermilion Dam) on the mainstem Vermilion River; Ellsworth Park Dam on the North Fork, 1.1 mi upstream of the Danville Dam; Aqua Illinois Dam (or Waterworks Dam) on the North Fork 2.4 mi upstream of the Ellsworth Park Dam; and Lake Vermilion Dam on the North Fork, 2.5 mi upstream of the Aqua Illinois Dam (Tiemann 2008; Csiki and Rhoads 2014; Tiemann et al. 2016). The Illinois Department of Natural Resources approved removal of two of these dams – the Danville Dam and the Ellsworth Dam. The Danville Dam was removed during the summer and autumn of 2018, whereas the Ellsworth Dam is scheduled to be removed in 2019.

Surveys for fishes (e.g., Hastings et al. 2016; Smith et al. 2017) and freshwater mussels (Tiemann et al. 2016) were conducted in the vicinity of the Danville Dam and Ellsworth Dam prior to removal. These surveys serve as the base for pre-removal conditions, and will be compared to post-construction surveys. These surveys showed a stark difference between riverine-type assemblages in the free-flowing areas and more tolerant oriented species in the impounded regions (Hastings et al. 2016; Tiemann et al. 2016; Smith et al. 2017).

Per the signed Incidental Take Authorization (ITA) and Implementing Agreement (IA) for the incidental take of the state-endangered Bluebreast Darter (Etheostoma camurum), Bigeye Chub (Hybopsis amblops), and Wavyrayed Lampmussel (Lampsilis fasciola), and state-threatened Eastern Sand Darter (Ammocrypta pellucidum), River Redhorse (Moxostoma carinatum), and Black Sandshell (Ligumia recta), the Illinois Department of Natural Resources (IDNR) requested fishes and freshwater mussels be salvaged from the construction zone of these dams. This report summarizes the fish and mussel relocations following the removal of the Danville Dam.

PROJECT LOCATION Prior to its removal, the Danville Dam (Figures 1-2) was located on the mainstem Vermilion River in Danville, Vermilion County, Illinois (Latitude 40.12234° N, Longitude 87.63158° W). The former impoundment expanded approximately 1.5 miles upstream (upstream boundary approximately Latitude 40.11957° N, Longitude 87.65272° W).

METHODS Demolition on the Danville Dam began on 18 July 2018. Over the next few weeks, crews from Halverson Construction Company, Inc. notched and removed portions of the dam, built a causeway, and stabilized the stream banks (Figure 3). During these time periods, staff from Illinois Natural History Survey (INHS) and volunteers from Eastern Illinois University (EIU) began salvaging fishes and freshwater mussels from the construction zone. Fishes and mussels were collected by hand (e.g., visual detection such as trails, siphons, and exposed shell – Figure 4). Given the size of the impounded area (~1.5 river miles), INHS and EIU personnel traversed the stream via kayaks looking for recently exposed areas. As water levels receded (Figure 5), stranded live animals were relocated to deeper waters, whereas deceased animals were noted (a subsample of deceased mussels were returned to the INHS Mollusk Collection, Champaign).

Nomenclature discussed in this report follows Page and Burr (2011) for fishes and Williams et al. (2017) for freshwater mussels. The current list of threatened and endangered species is taken from the Illinois Endangered Species Protection Board (IESPB) (2015).

RESULTS AND DISCUSSION One Smallmouth Bass (Micropterus dolomieu) was rescued during the construction project. This individual was in the old fish ladder, adjacent to the Danville Dam, immediately prior to construction on 18 July 2018. It was removed from the fish ladder and released downstream as heavy machinery was being mobilized to the dam. One Shorthead Redhorse1 (Moxostoma macrolepidotum) could not be rescued during the project. It was seen swimming into the fish ladder during the initial breaching of the dam. Given the safety aspect (e.g., heavy machinery actively jack-hammering and knocking down concrete), no attempts were made to rescue the fish. No other fish were collected or observed dead during construction activities. Neither the Smallmouth Bass nor the Shorthead Redhorse is listed as endangered or threatened at the state or federal level (IESPB 2015).

Eight attempts were made to salvage freshwater mussels (Table 1). During these surveys, 905 live individuals representing 23 species were relocated to deeper portions of the river as water levels receded (Table 1). This total includes state-threatened Purple Wartyback (Cyclonaias tuberculata; n=1) and Little Spectaclecase (Villosa lienosa; n=1) and state endangered Wavyrayed Lampmussel (Lampsilis fasciola; n=6) and Rainbow (Villosa iris; n=1) (Figure 6). No other state-listed mussels were collected live. The most common species collected were Mapleleaf (Quadrula quadrula, 264 individuals, 29% of total), Giant Floater (Pyganodon grandis, 217 individuals, 24% of total), Fragile Papershell (Leptodea fragilis, 130 individuals, 14% of total), Pink Heelsplitter (Potamilus alatus, 91 individuals, 10% of total), and Plain Pocketbook (Lampsilis cardium, 86 individuals, 9.5% of total). The remaining 18 species accounted for only 13% of the total individuals collected (Table 1). Mapleleaf, Giant Floater, Pink Heelsplitter, and Plain Pocketbook are among the most common species in the Vermilion River mainstem

1Whilenotcollected,thisindividualleaptoutofthewaterandontotheshoreasconcretefellintothefishladder.Avisualidentification(e.g.,headshapeandfincolor)wasmadeasthefishlaidonthebank.

(Stodola et al. 2013), and are tolerant of many hydrologic conditions, including impoundments (Watters et al. 2009). Pink Heelsplitter is a species that seems to have recently colonized the Vermilion River basin (Stodola et al. 2013).

Three state-listed species not covered under the ITA were collected – Purple Wartyback, Rainbow, and Little Spectaclecase. Purple Wartyback is found throughout the Vermilion River basin, and the individual collected during the dam removal was found in the North Fork, upstream of the boat launch (approximately Latitude 40.12258° N, Longitude 87.64142° W), in an area impounded prior to the Danville Dam removal. Neither the Little Spectaclecase nor the Rainbow has been collected alive from the mainstem Vermilion River in more than 50 years (INHS Mollusk Collection database 2018). The live and fresh-dead Rainbow were found in the mainstem at the Illinois Route 1 / US Highway 150 bridge underneath slab rock (approximately Latitude 40.12222° N, Longitude 87.63563° W), whereas the Little Spectaclecase was collected upstream at the railroad bridge (approximately Latitude 40.11586° N, Longitude 87.64744° W). These latter two species were surprising given that the Rainbow prefers flowing waters, and the Little Spectaclecase is most often found in smaller streams (Watters et al. 2009). One side effect of dam removal is stranding, desiccation, and predation of mussels within the former impounded areas (Sethi et al. 2004). In addition to the live individuals, 116 fresh-dead individuals representing 18 species were observed (Table 1), including 1 Purple Wartyback, 2 Wavyrayed Lampmussel, and 1 Rainbow. The majority of fresh-dead individuals appeared to have perished because they were stranded on a gravel bar or sandy run as water levels receded. Nearly half of these individuals (e.g., 41 Giant Floaters, 7 Mapleleaf, and 3 Plain Pocketbook) were observed during the sampling event on October 27th and were found on the gravel bar that formed at the mouth of the North Fork. Sometime between October 27th and August 13th, the old Illinois Route 1 bridge, which was acting as a barrier after the removal of the Danville Dam (Figure 7), was demolished, causing the river levels to drop. Additionally, INHS personnel observed local fisherman collecting stranded mussels near the old Illinois Route 1 bridge to use as fishing bait. Fisherman used hammers to break the shells and mussel tissues were threaded on hooks. At least one Pink Heelsplitter was observed being used for bait, though it is likely that others were collected and used for bait by fisherman when INHS personnel were not present.

Throughout the project, all attempts were made to mobilize a crew and relocate mussels within a day after Halverson Construction Company, Inc. removed a portion of the dam. Attempting to coordinate schedules, coupled with an above average rainfall year / water levels (Figure 8), made this task difficult and sometimes unproductive. As of the time of this report, the causeway at the old Danville Dam had not been removed. It is likely water levels could drop more as the causeway is being removed. However, mussels, being ectotherms, have likely buried deep into the substrate during the winter months.

Post-removal monitoring is planned, which will allow for appropriate evaluation of changes in the fish and freshwater mussel fauna following dam removal. Given time, fishes and mussels should naturally recolonize the former impounded areas of the Danville Dam if habitat conditions are optimal and source populations are in close proximity (Sietman et al. 2001; Tiemann et al. 2007; Tiemann et al. 2016).

ACKNOWLEDGMENTS Allison Sieja (INHS), Kirk Stodola (INHS), Cassi Carpenter (WIU), Taylor Fagin (EIU), and Reuben Frey (EIU) assisted in the field. Trent Thomas (IDNR) was instrumental in project activities. Rob Pruitt (Halverson Construction Company, Inc.) assisted in coordinating sampling logistics.

LITERATURE CITED Baxter, R.M. 1977. Environmental effects of dams and impoundments. Annual Review of Ecology

and Systematics 8:255-283.

Burroughs, B.A., D.B. Hayes, and K.D. Klomp, J.F. Hansen, and Jessica Mistak. 2009. Effects of Stronach Dam removal on fluvial geomorphology in the Pine River, Michigan, United States. Geomorphology 110:96-107.

Catalano, M.J., M.A. Bozek, and T.D. Pellett. 2007. Effects of dam removal on fish assemblage structure and spatial distributions in the Baraboo River, Wisconsin. North American Journal of Fisheries Management 27:519-530.

Csiki S., and B.L. Rhoads. 2010. Hydraulic and geomorphological effects of run-of-river dams. Progress in Physical Geography 34:755-780.

Csiki, S.J.C. and B.L. Rhoads. 2014. Influence of four run-of-river dams on channel morphology and sediment characteristics in Illinois, USA. Geomorphology 206:215-229.

Dean, J., D. Edds, D. Gillette, J. Howard, S. Sherraden, and J. Tiemann. 2002. Effects of lowhead dams on freshwater mussels in the Neosho River, Kansas. Transactions of the Kansas Academy of Science 105:232-240.

Dunn, H.L. and B.E. Sietman. 1997. Guidelines used in four geographically diverse unionid relocations. pp. 176-183 in K.S. Cummings, A.C. Buchanan, C.A. Mayer, and T.J. Naimo, eds. Conservation and management of freshwater mussels II: Initiatives for the future. Proceedings of a UMRCC Symposium, 16-18 October 1995, St. Louis, MO. Upper Mississippi River Conservation Committee, Rock Island, IL. 293 pp.

Hastings, R.P., S.J. Meiners, R.E. Colombo & T.E. Thomas. 2016. Contrasting impacts of dams on the metacommunity structure of fish and macroinvertebrate assemblages. North American Journal of Fisheries Management 36:1358-1367.

Illinois Endangered Species Protection Board (IESPB). 2015. Checklist of endangered and threatened animals and plants of Illinois. Illinois Endangered Species Protection Board, Springfield, Illinois. 18 pp. Published online at http://www.dnr.state.il.us/espb/index.htm.

Illinois Natural History Survey (INHS) Mollusk Collection data. 2018. http://biocoll.inhs.illinois.edu/portalx/index.php. Accessed on November 18.

Kanehl, P.D., J. Lyons, and J.E. Nelson. 1997. Changes in the habitat and fish community of the Milwaukee River, Wisconsin, following removal of the Woolen Mills Dam. North American Journal of Fisheries Management 17:387-400.

Maloney, K.O., H.R. Dodd, S.E. Butler, and D.H. Wahl. 2008. Changes in macroinvertebrate and fish assemblage in a medium-sized river following a breach of a low-head dam. Freshwater Biology 53:1055-1068.

Page, L.M. and B.M. Burr. 2011. Peterson Field Guide to Freshwater Fishes of North America North of Mexico. Houghton Mifflin Harcourt, Boston. xix + 663 pp.

Santucci, V.J., S.R. Gephard, and S.M. Pescitelli. 2005. Effects of multiple low-head dams on fish, macroinvertebrates, habitat, and water quality in the Fox River, Illinois. North American Journal of Fisheries Management 25:975-992.

Sethi, S.A., A.R. Selle, M.W. Doyle, E.H. Stanley, and H.E. Kitchel. 2004. Response of unionid mussels to dam removal in Koshkonong Creek, Wisconsin (USA). Hydrobiologia 525, 157-165.

Slawski, T.M., F.M. Veraldi, S.M. Pescitelli, and M.J. Pauers. 2008. Effects of tributary spatial position, urbanization, and multiple low-head dams on warmwater fish community structure in a Midwestern stream. North American Journal of Fisheries Management 28:1020-1035.

Smith, S.C.F., S.J. Meiners, R.P. Hastins, T. Thomas, and R.E. Colombo. 2017. Low-head dam impacts on habitat and the functional composition of fish communities. River Research and Application 33:680-689.

Stodola, A.P., S.A. Bales, and D.K. Shasteen. 2013. Freshwater mussels of the Vermilion and Little Vermilion Rivers of the Wabash River in Illinois. Illinois Natural History Survey Technical Report 2013(27). 26 pp + appendix.

Tiemann, J.S., D.P. Gillette, M.L. Wildhaber, and D.R. Edds. 2004. Effects of lowhead dams on riffle-dwelling fishes and macroinvertebrates in a Midwestern river. Transactions of the American Fisheries Society 133:705-717.

Tiemann, J.S., H.R. Dodd, N. Owens, and D.H. Wahl. 2007. Effects of lowhead dams on unionids in the Fox River, Illinois. Northeastern Naturalist 14:125-138.

Tiemann, J.S., S.A. Douglass, A.P. Stodola, and K.S. Cummings. 2016. Effects of lowhead dams on the freshwater mussel fauna in the Vermilion River basin, Illinois, with comments on a natural dam removal. Transactions of the Illinois State Academy of Science 109:1-7.

Watters, G.T. 1996. Small dams as barriers to freshwater mussels (Bivalvia, Unionoida) and their hosts. Biological Conservation 75:79-85.

Watters, G.T. M.A. Hoggarth, and D.H. Stansbery. 2009. The freshwater mussels of Ohio. The Ohio State University Press, Columbus. 412 pp.

Williams, J.D., A.E. Bogan, R.S. Butler, K.S. Cummings, J.T. Garner, J.L. Harris, N.A. Johnson, and G.T. Watters. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20: 33-58.

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Table 1. List of freshwater mussels recorded by date from the Danville Dam impoundment, Danville, Vermilion County, Illinois, as the dam was being removed during the summer and autumn of 2018. Data from these surveys include the number of individuals found alive (L) and those found as fresh-dead (D - likely perished as the result of being stranded as water levels receded). Special designation includes those species listed as either state-endangered (SE) or state-threatened in Illinois (ST).

____________________________________________________________________________________________________________ Scientific name Common name Jul 19 Jul 21 Jul 24 Jul 27 Jul 29 Aug 3 Aug 13 Oct 27 Total

Amblema plicata Threeridge 1 L

1 L

Anodontoides ferussacianus Cylindrical Papershell 1 L

1 L

Cyclonaias pustulosa Pimpleback 4 L 1 L 1 D

1 L 3 L

9 L 1 D

Cyclonaias tuberculata ST Purple Wartyback 1 D

1 L

1 L 1 D

Fusconaia flava Wabash Pigtoe 6 L 4 L 2 L 3 L 1 L 1 D

16 L 1 D

Lampsilis cardium Plain Pocketbook 19 L 1 L 25 L 14 L 1 D

15 L 10 L 1 L 1 L 3 D

86 L 4 D

Lampsilis fasciola SE Wavyrayed Lampmussel 1 L 1 D

3 L 1 L 1 L 1 D

6 L 2 D

Lampsilis siliquoidea Fatmucket 1 L 9 L 1 L 1 D

1 L 2 D

2 L 2 L 2 L

18 L 3 D

Lasmigona complanata White Heelsplitter 1 L 1 L 1 L

3 L

Lasmigona costata Flutedshell 1 L 2L 2 L 2 D

5 L 2 D

Leptodea fragilis Fragile Papershell 10 L 78 L 26 L 7 D

1 L 13 L 11 D

1 L 1 L

130 L 18 D

Potamilus alatus Pink Heelsplitter 50 L 20 L 3 D

4 D

17 L 4 D

4 L

91 L 11 D

Potamilus ohiensis Pink Papershell 1 L 1 L

2 L

Pyganodon grandis Giant Floater 24 L 4 L 132 L 25 L 3 D

4 L 19 L 6 D

7 L 2 L 41 D

217 L 50 D

Quadrula quadrula Mapleleaf 25 L 7 L 116 L 74 L 18 L 24 L 1 D

7 D

264 L 8 D

Strophitus undulatus Creeper 1 L 1 D

1 L 1 D

2 L 2 D

Theliderma metanevra Monkeyface 1 L 1 L 1 D

2 L 1 D

Toxolasma parvum Lilliput 1 D

8 L 1 L 1 L

10 L 1 D

Tritogonia verrucosa Pistolgrip 4 L 1 D

7 L 4 L 1 D

1 L 1 D

1 D

16 L 4 D

Truncilla truncata Deertoe 3 L 14 L 2 L 1 D

3 L 3 D

22 L 4 D

Utterbackia imbecillis Paper Pondshell 1 D

1 L 1 D

1 L 2 D

Villosa iris SE Rainbow 1L 1 D

1 L 1 D

Villosa lienosa ST Little Spectaclecase 1 L

1 L

Effort (person hours) 4 2 21 7 2 5 1 2 44 Number of individuals 100 L

4 D 12 L 2 D

455 L 175 L 16 D

43 L 8 D

98 L 30 D

15 L 7 L 56 D

905 L 116 D

Total number of extant species 15 5 19 16 10 15 5 10 23

Figure 1. The Danville Dam, prior to its removal, was located on the mainstem Vermilion River

in Danville, Vermilion County, Illinois – Latitude 40.12234° N, Longitude 87.63158° W (J.S. Tiemann photos).

Figure 2. Map of the Danville Dam, Danville, Vermilion County Illinois. Depicted are the former Danville Dam and its impounded waters, the Ellsworth Dam, and locations where state-listed species were collected within the project area (map by A.P. Stodola).

A) B)

C) D)

Figure 3. Images from the Danville Dam removal process – which include the notching and building of a causeway into the river – throughout the project duration: A) 19 July 2018; B) 29 July 2018; C) 13 August 2018; and D) 3 September 2018 (J.S. Tiemann photos).

Figure 4. Trails left by freshwater mussels in the Vermilion River as the water levels receded during the removal of the Danville Dam (J.S. Tiemann [top], R.M. Vinsel [bottom left], and A.P. Stodola [bottom right] photos).

Figure 5. Lower end of the impounded area created by the Danville Dam on the Vermilion River. Pictures – taken from the Illinois Route 1 / US Highway 150 bridge, facing downstream in an easterly direction – were shot on 18 July 2018 (top) and 29 July 2018 (bottom). The Danville Dam was approximately 300 yards downstream of this location (J.S. Tiemann photo).

A) B)

C) D)

Figure 6. The state-listed freshwater mussels collected from the impounded area during the removal of the Danville Dam: A) Purple Wartyback (Cyclonaias tuberculata) – threatened; B) Little Spectaclecase (Villosa lienosa) – threatened; C) Wavyrayed Lampmussel (Lampsilis fasciola) – endangered; and D) Rainbow (Villosa iris) – endangered (R.M. Vinsel photos).

Figure 7. The old Illinois Route 1 bridge – resting directly underneath the current Illinois Route 1 / US Highway 150 bridge – was revealed after the Danville Dam was notched and its impounded waters were partially drained. Like the Danville Dam, the old bridge was removed after from the river channel (J.S. Tiemann [top] and R.M. Vinsel [bottom] photos).

Figure 8. Hydrograph of the Vermilion River from the USGS gage (#033390002) near Danville (located ~2 river-miles downstream of the former Danville Dam). Top image shows four instances when the dam notching appeared on the hydrograph (July 18th, 23rd, 24th, and 25th), and bottom image shows above average discharge in September and October.

2https://waterdata.usgs.gov/il/nwis/uv?site_no=03339000