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Twomile Canyon Creek ditch. During flood conditions, the creek overflows the ditch and flows into Goose Creek. Twomile Canyon Creek starts in the mountains west of Boulder near Pine Brook Hill Fire Station. About one mile downstream, the stream channel becomes undefined west of Broadway. The overall study reach is estimated to be 3 miles. The drainage basin of the upstream reach is narrow, steep and rocky. The channel is two to three feet wide and well defined with steep banks. There are rocks and heavy vegetation within the channel which restrict the capacity. Wonderland Creek Approximately 1500 feet downstream the drainage basin becomes much wider between steep mountains. The creek remains highly vegetated, but becomes much wider through this section as it enters a pond east of Spring Valley Road Reservoir. Downstream the creek enters the City of Boulder southwest of Maxwell Reservoir. As the stream continues downstream, the drainageway becomes less steep and broader. This change coincides with an increase in urbanization over the middle sections of the basin. The Wonderland Creek drainage basin flows from Wonderland Lake and drains into Boulder Creek 4000 feet southeast of the Boulder Airport. The overall basin length is estimated to be 3.6 miles. The basin east of Wonderland Lake is very broad. Vegetation within this section consists of dense grasses with few trees. The drainage basin is developed within the Boulder City limits. East of Folsom, the drainage basin again becomes broad, and land development is more sparse. This broad and grassy basin pattern continues across 28th Street. As the basin drains eastward, it passes through Aspen Grove Subdivision. There are several high density developments from this pOint to Valmont Road. The remainder of the basin to the southeast is undeveloped. Elmer's TlfOItile Creek- As the stream leaves Wonderland Lake, the stream bed is narrow, approximately 3 to 4 feet wide. The creek banks are low, approximately 1 to 3 feet high. The stream flows through the Wildwood Solar Homes complex. The stream is narrow but well defined within this area. Southeast of the complex, the channe~ becomes grassy, with small rocks on the stream bottom. Banks are generally 4 feet high, with stone or rip-rapped embankments of up to 10 feet at street crossings. Further downstream in lower lying areas, the channel is laden with small stones, silt, and clay. Ponding occurs south of Iris Avenue at 47th Street. The subse- quent outflow has created a channel approximately 12 to 15 feet wide. South of Valmont, regrading has taken place which allows most of the flows in exceSs of the channel capacity to spill into the improved North Goose Creek channel. To the west of the intersection of Broadway with Iris, the rocky creek bed is approximately three to four feet wide. East of this intersection the basin is broad and gentle in slope with the channel completely overgrown with heavy grasses. The drainage enters Goose Creek at Floral Avenue south of Valmont. Elmer's Twomile Creek drainage basin is located between Wonderland and Twomile Creek Basins, and is tributary to Goose Creek. This creek originates west of Kalmia Avenue and Folsom. A short reach of the channel is concrete lined and bound by riprap. A natural earthen channel runs through Parkside Park, west of Folsom. The drainageway of this reach is approximately five feet wide and completely covered with vegetation. Beyond the park. the channel widens and remains heavily vegetated as it passes by the Whispering Pines condominium complex. The creek crosses Iris and passes through a series of 3 detention pondS behind the K-Mart and then crosses Glenwood Drive and Valmont. Under normal conditions, the creek flows into Boulder and Whiterods Drainage Ditch south of the Goose Creek confluence with the same Fourmile Canyon Creek The upstream drainage basin of Fourmile Canyon Creek originates near Sunshine Saddle in steep and rocky terrain. The basin is narrow in the foothills, but becomes less steep and wide as the drainageway extends to the east. The overall length of the basin is estimated to be 6.5 miles. The creek empties into Boulder Creek 3000 feet north of Valmont Butte. 4