Arroyo Seco Watershed Restoration Feasibility Study Volume I Project Report May 31, 2002 Prepared for: California Coastal Conservancy 11th Floor, 1330 Broadway Oakland, CA 94612 Prepared By: North East Trees 570 W. Avenue 26, Suite 200 Los Angeles, CA 90065 Arroyo Seco Foundation 539 East Villa St. #2 Pasadena, CA 91101 Table of Contents Acknowledgments .................................................................................................. i-1 I. Introduction .......................................................................................................... I-1 A. Project Description ............................................................... I-1 B. Watershed Description ......................................................... I-2 C. Restoration Vision, Goals and Guidelines ......................... I-11 1. Vision..................................................................................... I-11 2. Goals and Guidelines ........................................................... I-12 D. Related Planning Studies ................................................... I-13 E. Project Process..................................................................... I-13 1. Public Process....................................................................... I-15 a. Agency Coordination ..................................................... I-15 b. Stakeholder and Community Process........................... I-16 i. Stakeholder Meetings ................................................ I-16 ii. Community Meetings .............................................. I-17 c. Outreach and Media....................................................... I-17 2. Data Collection ..................................................................... I-18 a. Potential Contacts .......................................................... I-18 b. Documents ...................................................................... I-18 c. Geographic Information Systems (GIS) Data ............... I-19 d. Data Gap Analysis .......................................................... I-19 3. Phase I Initial Planning Investigation .................................I-21 4. Phase II Research and Recommendations Development .. I-23 II. The Arroyo Seco Watershed: An Historic Overview ............................ II-1 A. Landscape Structure ............................................................ II-2 1. Geologic Structure and Topography .................................... II-2 a. Mountainous Upper Watershed ..................................... II-2 b. Lower Arroyo ................................................................... II-4 2. Soils ....................................................................................... II-4 3. Hydrology.............................................................................. II-4 i. Climate ............................................................................. II-5 ii. Surface Hydrology .......................................................... II-5 iii. Groundwater ................................................................... II-7 4. Habitat/Vegetation.............................................................. II-10 B. Landscape Functions .......................................................... II-10 1. Geomorphology & Flows of Sediment .............................. II-11 2. Flows of Water ..................................................................... II-11 3. Flows of Wildlife ................................................................. II-11 Table of Contents a 4. Flows of Energy ................................................................... II-12 5. Flows of Fire ........................................................................ II-12 C. Landscape Change through Time ..................................... II-15 1. Pre-European Settlement.................................................... II-15 2. The Mission & Rancho Eras ................................................ II-15 3. The Agricultural Period ...................................................... II-16 4. Urban/Suburban Period ..................................................... II-18 D. Conclusion ....................................................................... II-19 III. Current Conditions and Function in the Arroyo Seco Watershed III-1 A. Landscape Structure - Human Practices and Disturbances III-1 1. Geology & Soils .................................................................... III-1 2. Hydrology............................................................................. III-2 a. Water Supply, Surface and Groundwater Structure ...... III-2 b. Water Quality Structure ................................................. III-3 3. Habitat Structure.................................................................. III-4 B. Landscape Function - Effects on Watershed Function ....... III-7 1. Geomorphology & Sedimentation ..................................... III-7 2. Hydrology............................................................................. III-8 a. Water Supply, Surface and Groundwater Function ...... III-8 b. Water Quality Function ............................................... III-10 3. Habitat Function................................................................ III-11 C. Change Over Time (Current Land Use) ........................... III-12 1. Open Space & Recreation ..................................................III-13 a. Upper Watershed ..........................................................III-14 b. Lower Watershed ..........................................................III-14 i. City of La Cañada Flintridge.................................III-14 ii. Community of Altadena (Los Angeles County)..III-16 iii. City of Pasadena....................................................III-16 iv. City of South Pasadena .........................................III-17 v. City of Los Angeles Communities (Highland Park, Mount Washington, Montecito Heights, Lincoln Heights, Cypress Park) ..........................................III-18 D. Conclusion ....................................................................... III-19 IV. RESTORING THE WATERSHED: Feasibility and Planning Recommendations ............................................................................................ IV-1 A. Restoration Feasibility & Watershed Roles .........................IV-2 1. Feasibility ............................................................................. IV-2 2. Roles of Upper Watershed ................................................... IV-3 3. Roles of Lower Watershed ................................................... IV-4 B. Restoration Vision Components.........................................IV-5 b Arroyo Seco Watershed Restoration Feasibility Study 1. Arroyo Seco Stream Corridor Naturalization..................... IV-7 a. The Arroyo Seco Stream Corridor .......................... IV-7 b. Arroyo Seco Tributaries in both the Upper and Lower Watershed..................................................... IV-7 c. Flood Attenuation ................................................... IV-8 d. Storm Water Runoff Detention & Filtration ......... IV-8 e. Surface Stream Flows .............................................. IV-9 f. Sediment Transport ................................................. IV-9 2. Water Quality ....................................................................... IV-9 3. Native Habitat ...................................................................... IV-9 4. Recreation ........................................................................... IV-10 5. Open Space ........................................................................ IV-10 C. Framework for Restoration Projects: Watershed Restoration Goals, Guidelines & Action Items ..................................... IV-11 D. Recommendations for Projects and Programs .................IV-14 E. Next Steps ..........................................................................IV-27 1. US Army Corps of Engineers Reconnaissance Study ....... IV-27 2. Proposition 13/CalFed Grants .......................................... IV-28 3. Ongoing Coordination ..................................................... IV-28 4. Implementation of Projects .............................................. IV-28 F. Conclusions .......................................................................IV-28 V. References ............................................................................................................. V-1 Table of Contents c Table of Illustrations Figure I-1: Location Map ............................................................ I-3 Figure I-2: Arroyo Seco Watershed ............................................ I-4 Figure I-3: Topographic Relief ................................................... I-5 Figure I-4a: Elected Official Boundaries 1 ................................ I-6 Figure I-4b: Elected Official Boundaries 2 ................................ I-7 Figure i-5: Arroyo Seco Cultural & Open Space Map ................ I-9 Figure I-6: Points of Interest ................................................... I-10 Table I-1: Related Studies ......................................................... I-13 Figure I-7: Capital Projects ...................................................... I-15 Table 1-2: Participating Agencies & Representatives ............... I-15 Table I-3: Critical Resource Bibliography ................................ I-19 Table I-4: Critical Map Layers (GIS) .......................................