Developing The Stormwater Master Plan

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Following is a description of the important data and their potential uses in developing the Stormwater Master Plan: a) The accuracy and resolution of topographic data that determines the drainage area boundaries, slopes and flow paths have a significant impact on the quality of hydrologic and hydraulic modeling and flood mapping. The FMC team expects that the high quality topographic data of Freetown, including the upstream mountainous areas, will be provided by SLRA within a week of the project inception. A basemap showing ortho-rectified aerial imagery will significantly help in ground truthing and resolving discrepancies in data. Additionally topographic survey will be required to determine the centerline of existing and proposed storm drain alignment and establish vertical and horizontal geometric characteristic of the urban storm water drainages and structures, centerlines and cross sections. b) Geographic coordinates of significant features on or adjacent to the urban storm water drainages and structures, including buildings, markets and roads will be required. It is assumed that such GIS data are readily available to support the development of the Master Plan. c) Assuming the long-term rainfall data are readily available from the Meteorological Office, all rainfall records from local rain gauges will be compiled. The rainfall data should have a time interval of one hour or less. The rainfall records will be used as input to the model and to determine the peak flows
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