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I I I I I I I I I I I I I I I I I I I Floodplain Mappin2: The hydraulic analysis indicates flood depths less than one foot are expected within the Town during the 100-year event of North Branch Conejos River. The photograph on the cover page of this report was obtained from web site www.city-data.com/city/Manassa- Colorado.html, Owner www.slbdwel1er.com and provides an idea of the depth of flooding which could be experienced in the Town during the 100-year event. FEMA indicates areas of 1 per cent annual chance flood with average depths of less than I foot be designated as Zone X It is assumed much of the Town will be in this Zone as noted on the Floodplain Delineation Map, Figure 5. This report recommends the Zone A FEMA designation for part of the Town on the FIRM, which includes "special hazard areas subject to inundation by the 1 percent annual chance flood event", is removed from Manassa for the purposes of CWCB. The degree of shallow flooding within Manassa from North Branch Conejos River during the 100-year flood is anticipated to be less than the depth of flooding allowed on local, collector, and minor arterial streets during the 100-year flood following standard engineering practice (typically 18-inches at the gutter flowline for streets constructed with curb and gutter or 6-inches at the street crown for streets constructed with roadside ditches). Thus, only minor damage is anticipated in the Town during the 100-year flood of North Branch Conejos River. Structures which are located within low points or sumps which are below the normal grade of the Town could experience more serious damage. FEMA requires a detailed floodplain analysis for development projects greater than 5 acres in area or more than 50 units in size in 'approximate floodplains be performed by a professional engineer. Vertical datum for the FIRM and FrS is NGVD 1929. To convert to the most recent standard, NA VD 1988, add 4.01 feet to all elevations (USCOE, 2000). 6