Environmental group Heal the Bay released their long awaited study on the state of the Malibu Creek Watershed. The study is based on water quality and stream ecology monitoring data from over a 12 year period. Also included in the study is a quantitative assessment of the physical changes to Malibu Creek and its tributaries including stream bank armoring, stormdrain outfalls, dump sites, invasive vegetation, erosion and sedimentation, and other parameters.
The major findings from the report included: subwatersheds with greater than 3.5% impervious area started exhibited signs of water quality and ecological degradation. At over 6.5% Impervious area the degradation became severe (high nitrate, phosphate and fecal indicator bacteria levels, severe algal growth, and very low Index of Biotic Integrity levels); approximately one fifth to one third of 70 miles of stream mapped in the watershed had stream hardening, stream bank degradation or failure, nearby stormdrain outfalls, invasive vegetation, dump sites and sedimentation and erosion problems; Reference locations above urban development had much better water quality and ecological health than sites below urbanized areas or at the mouths of tributaries; High nitrate and phosphate concentrations were found downstream of urbanized or agricultural areas. Also, during the winter months, the highest nutrient concentrations in the watershed were found directly downstream of the Tapia Water Reclamation Facility which only discharges during the wet season; Researchers developed a stream health index based on numerous parameters that helped identify the most degraded subwatersheds within the Malibu Creek watershed; Also, researchers documented the invasion of the New Zealand Mud Snail and the subsequent spread of the invasive algae eating snail. They also attempted to assess the impacts of the invasion on stream health.
The monitoring effort was largely performed by volunteers that donated tens of thousands of hours since the late 1990s. Authors of the report included Shelley Luce (completed her Environmental Science and Engineering doctorate based on Stream Team results) and Katherine Pease who received their doctorates at UCLA, environmental science graduate, Sarah Diringer, Mark Abramson (program creator and long time manager),Sarah Sikich, and Mark Gold, IoES Coastal Center director. Learn more about the study and download the full report.