Rock River at Fort Atkinson (Excerpt from SIR 2008-5235)
The Rock River flows south and southwest through the community of Fort Atkinson in southern Jefferson County (appendix 7). The Rock River continues through Lake Koshkonong into Dane and Rock Counties. The reach ends at the USGS streamgage at Indianford, south of the town of Edgerton. The accuracy of the USGS high-water marks was corroborated with nearby high-water marks surveyed during the flood by Jefferson County officials. The streamgage recorded a flood-peak elevation of 782.5 ft. The surveyed elevation of the high-water mark on the streamgage house was 782.4 ft.
This reach of the Rock River and Lake Koshkonong covers three counties, which led to difficulties with matching digital datasets. Each county has high-resolution DEM available (3 m or better), but they did not match exactly along county lines. The reach was broken into three areas along the county boundaries in order to facilitate the modeling. The edges of the extent of modeled inundated area matched adequately and the three areas were merged (appendix 7B). The flood-depth grid could not be merged, so the results of
model runs for the three counties are presented separately in appendix 7C. Very little error was found in the modeled inundated area, and the small correction that was needed was due to recent construction on the north side of Lake Koshkonong and to some low-lying areas in South Fort Atkinson that were not in hydraulic connection with the floodwaters. The area south of Lake Koshkonong, near Edgerton, was not checked by city or county officials. The modeled and corrected inundation areas can be viewed as a good representation of the extent of flooding, but depths should be interpreted with caution, bearing in mind the limitation due to the use of digital data from the three counties.
Photo of streamgage 05427235 Rock River at Lake Koshkonong, August 19, 2008. Photo from USGS.
Appendix 7A. High-Water Mark Table (pdf) (excel) (shapefiles)
Appendix 7B. Flood-Peak Inundation Map (pdf) (shapefiles)
Appendix 7C. Flood-Depth Maps (pdf) (grids)
Appendix 7D. Flood-Peak Water-Surface Profile (pdf)
Link to real-time streamgage 05427235 Rock River at Lake Koshkonong, Wis
Link to real-time streamgage 05427570 Rock River at Indianford, Wis