Contemporary streamkeepers : a comparison of two urban horticultural restoration programs
- Author(s): Rowley, Charles
- et al.
This paper presents a comparison of the successes and failures associated with two urban creek restoration programs, one in northern California (Temescal Creek, Alameda County) and another in southern California (White Oak Creek, Ventura County). Both programs were undertaken in response to flood control planning needs in urbanizing areas. The Temescal Creek effort was initiated nearly 30 years ago while the White Oak Creek program was completed about four years ago. Based on success criteria developed by the author, it is evident that the more recent White Oak Creek program has resulted in significant success while the earlier Temescal Creek restoration has not achieved what are considered generally acceptable levels of success criteria. An explanation for the differential degree of restoration achievement is provided in this paper. This explanation can be summarized briefly as being attributable to the following changes in management and scientific practice over the past 30 years.
First, the legal basis for achieving successful restoration has changed substantially during this time period. Monitoring requirements imposed by wetland/riparian regulatory agencies have provided an effective platform to enforce sustained monitoring and to require modifications to horticultural programs that fail during the monitoring period. Conservation easements are now typically required to provide perpetual legal protection to habitat restoration oriented programs. Monitoring programs and their periodicity are critical to long-term restoration success--the author recommends that the standard annual monitoring frequencies adopted by state and federal regulatory agencies should be increased.
Second, it is evident that properly engineered low flow distribution structures between retention basins and downstream areas are critical to success. Without proper engineering and careful testing and monitoring of low flow diversions, the essential sources of water and nutrients for a successful restoration program cannot be insured. The introduction of constant low flow water to an urbanized stream converts ephemeral and intermittent streams to new "artificial" perennial systems. These new hydrologic conditions are prone to invasive plant dispersion and can impact the adaptability of indigenous vegetation. This situation further supports the need for on-going monitoring and maintenance through the use of conservation easements.
Finally, social and local government political factors also play a role in the process of whether a sustained program of streambed restoration will succeed or fail. Changing demographics and community values may alter the integrity of the approved plan over time. Understanding and properly anticipating urban design issues and population pressures on a restored streambed substantially influence whether a program will, in the long run, succeed or fail as an habitat restoration effort. Planning the transition from professional monitoring to community ‘Streamkeeper’ programs is one way to ensure reliable long term monitoring.