19 - Drainage Presentation - Sandy Creek Upper Tributaries 4 and 6

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Image 14: Combined Tributary: Large grass lined channel as it crosses under South Collegiate Drive. It is important to keep this maintained and flowing, as this acts as the main floodway (a channel for an overflow of water caused by flooding) for the creek downstream of the residential neighborhoods. Where we have the opportunity to widen this channel and place concrete blocks, it will help hydraulic functionality of the basin. 2016 Flood Event,: A large flood event occurred in the city on the week of April 30, 2016. According to the Cobb-Fendley Engineering Report, sponsored by the City Council after the event transpired, rain amounts over a narrow time period contributed to flooding. "On April 30, 2016, the City of Paris received 5.99 inches of rain. Over May 2 and May 3, the City received an additional 0.5 inches of rain. On May 9 and May 10, the City received an additional 5.04 inches of rain. This data was taken at Paris Cox Field airport and retrieved from the National Oceanic and Atmospheric Administration (NOAA) Global Historical Climatology Network... Significant flooding occurred after the April 30 rain event and again after the May 9 event. A total of 11.53 inches of rain fell over an 11 day period. " This has been characterized in media and local discussion as a 500 year flood recurrence interval. Each year, there is a 0.2% chance that this could happen. For reference a 100 year recurrence interval has a I% chance of happening each year. This event has been anecdotally conveyed from residents and business owners that areas that typically do not flood were flooded at least 2 times in 2016. Cobb-FendleyReort SummLiw The Engineering Firm Cobb-Fendley from Frisco, Texas developed a report on Tributaries 4 and 6 in between August 2017 and April 2018. The following is a series of excerpts from their executive summary and report. "Cobb Fendley performed an on -the -ground survey of Tributaries 4 and 6, collecting drainage culvert dimensions and channel cross-section data. The survey data was merged with surrounding lidar data for use in the hydraulic analysis. The existing floodplain model was obtained from the