San Juan Creek Watershed Stream Monitoring Program

South Orange County, CA

PACE prepared a Monitoring Plan to implement an Adaptive Management Program with respect to stream erosion and sedimentation within San Juan Creek based on field inspection and observations and quantitative monitoring / qualitative assessment for Rancho Mission Viejo Planning Area 1 (PA-1).  The objective of this Plan was to ensure the adjustments within the active floodplain of San Juan Creek are monitored in order to evaluate changes in stability of the streambed and streambanks consistent with California Environmental Quality Act (CEQA) commitments and conditions of approval.  The “active” portions of the floodplain system are the portion of the streambed and banks that experience the dominant discharge and the majority of the fluvial action, such as exposed sand streambed, active thalweg, and stream movement. This includes evaluating performing assessments of recorded stream data in order to evaluate the performance of the channel system, as well as implementing corrective procedures when needed. An adaptive approach to the monitoring program will fulfill the following purposes:

• • • Identify trends of the creek within and downstream of the project
    • Evaluate the response of the creek system to the development within the watershed
    • Assess long-term streambed and streambank stability or instabilities
    • Monitor impacts to public structures within the creek system
    • Application of qualitative and quantitative geomorphic and engineering techniques for evaluation of collected data

The stream monitoring data provides the foundation for a broad range of assessments, including:

• • • Monitoring trends in fluvial and geomorphic conditions in time
    • Quantifying impacts
    • Assessing stream and watershed response to different management activities
    • Change in the inventory of stream resources
    • Allowing valid comparisons of the stream system over time

Key Features:

• Hydromodification monitoring
• Field measurements
• Erosion cause and effect assessments
• Watershed Geographic Information System (GIS) assessment tools