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SECTION 2 Study Area Characteristics 2.5 Surface Water Features and Drainage System This section describes the existing drainage features of the basin including the City's stormwater facilities, open waterways, and wetlands. Refer to Map 5. 2.5.1 Waterways Pre - settlement (prior to 1855) morphological conditions in the Willamette Valley reflected a network of shallow, broad swales that would often over -bank during storm events creating ponded conditions. Today, most of the drainages have been altered into narrow, deep and well - defined channels where the management objective of preventing over banking conditions has been accomplished for most small storm events. Five major drainage systems exist in this basin including: the A -1 Channel, Flat Creek, Spring Creek, Highway 99 and the Willamette Overflow (also referred to as the East Santa Clara Waterway). Generally, these open waterways run in a northerly or northwesterly direction. Historically, most of these features meandered along the valley floor before reaching the Willamette River or Long Tom River. Some of these have been altered into narrow, deep and well defined channels designed to collect and convey runoff while others remain relatively undisturbed. 2.5.1.1 A -1 Channel The A -1 Channel originates at the junction of Beltline Highway and the Northwest Expressway. It is the largest waterway in this basin flowing northwesterly about three miles through the Highway 99 Industrial Corridor. The channel is surrounded by residential use in the Santa Clara neighborhood changing to adjacent agricultural use as it leaves the UGB. The channel drains into Amazon Creek outside of the Metro Plan boundary. This channel was constructed by the Soil Conservation Service as part of the Lower Amazon and Flat Creek Watershed Improvement Projects primarily for flood control purposes. Vegetation lacks diversity along the channel contributing to poor wildlife habitat. The channel has high enhancement potential however, due to its connectivity with other waterways. The A -1 Channel is listed as a riparian resource site (refer to E60: A -1 Channel) in the adopted 2007 Goal 5 Water Resources Conservation Plan, a refinement plan to the Eugene - Springfield Metro Plan. Protections for two of three identified segments of Site E60 in the form of the Water Resources Conservation Overlay Zone (Eugene Code 9.4910) were adopted by the City of Eugene in November 2005 (effective January 1, 2006) and Lane County in December 2006 (effective January 12, 2007), including setbacks of 20 feet from top of high bank. 2.5.1.2 Flat Creek The southern portion of Flat Creek begins near the Northwest Expressway and Park Avenue and flows north towards Beltline Road. With development of Beltline Road and the Northwest Expressway, the natural Flat Creek drainage area south of Beltline Road was diverted into the A- 1 Channel, and is no longer hydrologically linked to the northern portion of Flat Creek. The southern portion of Flat Creek includes riparian resource sites E61 (Middle Flat Creek) and E69 0:\25695978 Eugene RR -SC Final Basin P1an\Master P1anTINAL 2- 2010\Master_Plan 3- 11- 10_FINAL_ Word _Version.doc 2-14