Klotz Draft Report for Fairmont Park East and Brookglen 072809

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Mr. Ron Bottoms July 22, 2009 Page 2 of 12 facility located on it or upstream of it. During the recent flood event John Randolph with HCFCD noted that water from B 112-00-00 channel had overtopped the chanxiel and went over Spencer Road. The B 112-02-00 tributary is an earthen channel, does have a large HCFCD detention facility located upstream of Spencer Road and would be easier to improve and enlarge than removing the concrete within the B 112-00-00 channel. The slab elevations of the residential structures indicate that the slabs that were surveyed are all above the 100 year event flood levels from the receiving channel from the downstream areas of channel B112-00-00. However the tributary channel B112-02-00 does not have 100 year capacity but has high levels within the channel when B112-00-00 channel is flowing full. Field observations by City staff and from HCFCD indicate that the water from B112-02-00 cannot easily enter the main channel of B112-00-00 and thus creates a backwater effect within the Brookglen subdivision. Reducing the backwater effect of the B 112-02-00 channel on the Brookglen subdivision is the focus of this analysis. The issue that is being addressed in this report is if the B 112-02-00 channel were reconnected back to the B109-03-00 and B109-00-00 channel could the backwater effect in the Brookglen subdivision area be reduced enough to help the drainage with the subdivision. Also included with this analysis would be channel improvements and appropriate mitigation within the B 109-00-00 watershed to mitigate the diversion of the Brookglen subdivision area to B 109-00-00 channel. Purpose and Scope The purpose of this letter report is to identify benefits, downstream impacts and document changes in computed water surface elevations relating to possible diversion of Unit B 112-02-00 from Unit B 112-00-00 to Unit B 109-03-00. The following is the Scope of Services association with the project: 1. Prepare a broad based hydrologic analysis for the simulation of redirecting Tributary 1.78 to Willow Springs Bayou, or Unit B 112-02-00, to drain from west to east and disconnected Unit B 112-02-00 from Willow Springs Bayou, or Unit B 112-00-00. 2. Prepare a broad based hydraulic analysis for the simulation of redirecting the Tributary 1.78 to Willow Springs Bayou, or Unit B 112-02-00, to drain from west to east and disconnected Unit B 112-02-00 from Willow Springs Bayou, or Unit B 112-00-00.