Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />. <br /> <br />the 1993 flood. No flow measurements were made in any of these floods, so no frequency <br />estimates can be made. <br /> <br />Previous Studies and Proiects <br /> <br />Two floodplain information documents have been mentioned in this report. In May 1986 <br />Engineering Professionals, Inc. prepared a report entitled Town of Otis Master Drainage and <br />Flood Study. The report determined flood flows in Otis, delineated lO-year and 100-year <br />floodplain boundaries based on those flows, and proposed conceptual flood control elements to <br />address the problems that were identified. In January 1988 Norton, Underwood & Lamb designed <br />flood control and storm drainage improvements, as shown on a map entitled Project Layout, <br />Drainage and Floodplain Improvements. Those improvements were subsequently constructed to <br />improve conditions north of the crossing of the Southwest Drainage under the Burlington Northern <br />Railroad. While additional improvements were designed for the south side of Otis at the same <br />time, those improvements were not constructed. <br /> <br />The preparation of the Master Drainage and Flood Study in 1986 began the town's efforts to <br />address some of its flooding and storm drainage problems through construction of structural <br />improvements. In the northeastern portion of Otis a flood control project, shown in detail on the <br />Norton, Underwood & Lamb map, was completed in 1988. That project provided 100-year flood <br />capacity for the Southwest Drainage immediately downstream of the railroad crossing all the way to <br />the northeastern corporate limit of Otis. The project included channelization and the replacement of <br />culverts under Highway 34. In addition, storm drainage improvements which tie into the flood <br />control channel greatly reduced some localized ponding problems in the northern part of Otis and in <br />the northwestern part of Otis, near the high school. A swale was constructed along a portion of the <br />Northern Drainage to reduce the flood risk along the northern edge of Otis as a part of this project. <br />No changes were made at the railroad crossing except for some minor changes at the outlet. <br /> <br />The town has continued to attempt to reduce flooding and drainage problems in the area upstream <br />of the railroad crossing. Because the railroad crossing structures are such a severe constraint to <br />large flows, any improvements that do not increase the capacity under the railroad can only improve <br />conditions up to approximately a 7 -year frequency. At the time of this report the town and its <br />engineer, Mclaughlin Water Engineers, was working on such a project, with a design frequency of <br />approximately a 7-year flow. A channel with some concrete street crossing structures will be <br />constructed between two north-south streets, Washington and Vine. The project will not alter the <br />drainageway downstream of Vine, toward the railroad crossing, and it will not alter the drainageway <br />upstream of Washington, to the southwest. It will control floods up to a 7 -year magnitude, and it <br />will greatly accelerate the time for draining the "lake" that forms on the south side during bigger <br />floods. No measurable changes to the 100-year floodplain are expected as a result of this project. <br />The project should be complete in time for the flood season of2000. <br /> <br />4 <br />