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I I I I I I I I I I I I I I I I I I I Development along Tributary 2 is completely agricultural with the exception of a few oil and gas wells and related storage facilities. No resi denti a 1 development exi sts adjacent to thi s reach. Wi th the exception of the two streets, a small online reservoir, and ,some minor earthwork in a storage yard just west of Quebec Street, the Tributary 2 floodplain has experienced no significant encroachment. Tributary 3: The study reach for Tributary 3 begins at its confluence with the main stem (Cross Section No. 3.10) and ends about 900 feet downstream of East 144th Avenue (Cross Section No. 3.15). Floodplain limits and the water surface profile are shown on Sheets 3 and 17. average stream slope exceeds 1.5 percent, and will likely produce high velocities and erosion during flood flows. No stream crossings exist along the study reach of Tributary 3. The floodplain for this reach is well confined to the channel. The average stream slope approaches two percent and will likely produce high velocities and erosion during major events. The following paragraphs describe specific problem areas along Tri butary 2: 1. Both Monaco Street and Quebec Street are overtopped by 1 and 1.5 feet, respectively. Both overtoppings result from inadequate drainage culverts. Debris blockage is probably of greater concern for the smaller frequency events because the culvert capacities are very small compared to the 100-year flows. Both stream crossings are gravel roads, and therefore erosion and road washout potential from overtopping is high. Refer to Sheets 15 and 16. Development along Tributary 3 is mostly in the form of agricultural use, with some scattered areas of nati ve begetati on on undeveloped land. No significant floodplain encroachment has occurred along this study reach. Tributary 4: The study reach for Tributary 4 begins at its confluence with the main stem (Cross Section No. 4.10) and ends 1100 feet upstream of Quebec Street (Cross Section No. 4.55). Floodplain limits and the water surface profile of this reach are shown on Sheets 9 and 18 through 22. 2. A small onl i ne reservoi r exi sts just east of Monaco Street. The spillway for this reservoir is inadequate and in poor condition. The backwater created by this condition causes a rise in the water surface of about 6 feet above that level shown on the date of survey. Although the embankment is not overtopped, erosion potential is high. A small metal shed on the north side of the reservoir will sustain shallow flooding. Refer to Sheet 15. Stream crossings in this reach include Quebec Street, East 144th Avenue, Yosemite Street and a private road just upstream of Yosemite Street. The stream slope ranges from about 1.6 percent in the upper reach to less than 1 percent near the confluence with the main stem. Development along Tributary 4 is primarily agricultural. A few oil and gas wells are located in and adjacent to the stream. Except for the streets, three old existing reservoir embankments, and some apparent mi nor gradi ng work around one of the well faci 1 iti es, no significant floodplain encroachment has occurred along the 2.7 mile study reach. 17