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I I I I I I I I I I I I I I I I I I I 2.1 -,.>1'- crossing at Cemetery Road backs up the flood waters creating localized flooding. Tne two crossings proposed by the town, one between Lincoln and Village Roads and the other downstream from Watson Road, were assumed capable of passing the Inter- mediate Regional Flood, but not the Standard Project Flood. Greater flooding at those locations can be expected during the Standard Project Flood. These crossings are still in the planning stage and no engineering designs are available for review. Due to the wider flood plain, greater depth of flooding, higher velocity of flow and longer duration of flooding uring a Standard Project Flood, damage would be more extensive than during the Intermediate Regional Flood. Plates I~ through ~ show water surface profiles of the Intermediate Regional and the Standard Project Floods. Depth of flow in the channel can be estimated from these illustrations. Typical cross-sections of the floodplain at selected locations, together with water surface elevations and extent of both floods are shown on Plate 15. OBSTRUCTIONS As previously noted there are numerous obstructions to flood )s flow in the study area. Pertinent data on obstructive bridges t' ~~&nd culverts are contained in Table 3. As may be seen from Plates 0,.\-1 \,,\ 'I v v 3 through , the effect of obstructions is to raise the water S'/ ~~ surface elevation upstream; Obstructive bridges are especially susceptible to structural damage from the forces of floodwater and floating debris. VELOCITIES OF FLOW Occurrence of the Intermediate Regional and Standard Project Floods will result from the flows shown in Table 2. Channel bed velocities of both floods are on the order of 7 and 12 feet per second respectively, while overbank velocities average between 0.5 and 12 feet per second throughout most of the study area.