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f , 1 , - 21 - the water is out of the channel, a wide band of flooding through the town, paralleling the river, will occur. The flooding compounded by the Lincoln and Watson road crossings which, if plugged with debris, also will contribute to water leaving the channel. Several residences and commercial buildings will be affected by the flood waters. Most of the flood waters return to the channel below Watson Road and above French Gulch. ~ . f , ! Damage during the Standard Project Flood would be more extensive than during the Intermediate Regional Flood due to the wider floodplain, greater depth of flooding, higher velocity of flow, and longer duration of flooding. Plates 11 through 16 show water surface profiles of both the Inter- mediate Regional and Standard Project Floods. The depth of flow in the channel can be estimated from these illustrations as well as from the reference points in Table 4. These elevations refer to the water level in the Blue River channel which may differ from elevations in the town once the water has left the river channel. Sheet flooding within the town would generally not exceed a 2 foot depth. Typical cross- sections of the flood plain at selected locations are shown on Plate 17. In addition to the potential flood hazard from the Blue River there also exists a flood hazard from the tributaries within the town, such as Lehman and Illinois Gulches. The damages caused by a flood from the tributaries can equal or exceed the damages caused by a flood on the Blue River. OBSTRUCTIONS Bridges and culverts form obstructions to flood flows in the study area. Table 5 summarizes pertinent data on these obstructions. As may be seen from Plates 4 through 10, the effect of obstructions is to raise the water surface elevation upstream. Bridges are susceptible to structural ~ ~~~~-~-~~