There are some BIG paradigm shifts necessary for the way we professionals design and implement erosion control. Ow! Paradigm shifts can be painful. We have been presenting a new 2-day course on SUSTAINABLE EROSION CONTROL for Caltrans Landscape Architecture [Click here for more info]
Interesting concept eh? Sustainable.
The concept and design criteria require the shift in thinking - paradigm shift. To be sustainable our projects need to:
- Increase infiltration - more infiltration results in less runoff which results in less erosion from concentrated flows and less delivery of pollutants.
- Decrease concentrated flows - reduced "hydromodification" is necessary. For decades now (since the horse and buggy days when our storm sewers carried feces and garbage and other public health disease problems) the engineer has been responsible for " getting the stormwater out of here". This has resulted in increasingly degraded urban streams. What do we do? Answer; improve and manage the soil such that in every opportunity we increase infiltration and water holding capacity.
- Reduce compaction - Yup, paradigm shift!! Really now, you designers out there, take a good hard look at when the engineering properties of compaction is needed for the structures and roadways and when can the more natural factors, e.g., roots, soil aggradation, cohesion, even fungal hyphae, provide the needs soil stability.
- Use "native vegetation" - This criteria has several parts to it. Most importantly, natives have adapted to the geo-climactic regime and may not require huge inputs of energy, e.g., irrigation, maintenance, herbicides etc. Also, we need to choose plants allow for natural succession, so the project gets "stronger with time".
- Landform Grading - this design concept and engineering design is well described in "Landforming" by Horst J. Schor and Donald H. Gray, 2007, John Wiley & Sons. This concept is so important it will require an entire discussion in itself. But the Hollywood Hills projects really tells it all!!
Maybe we can cover more of these concepts and what SUSTAINABLE means to you later.
In the meantime lets look at a paradigm shift happening in Canada.
David Polster, a long-time practitioner of bioengineering and successional restoration from British Columbia, is always on the forefront of paradigm shifting. The problem up in the provinces (as you may recognize here also) is that the typical grass-type "restoration mixes" are doing great to prevent erosion in the short- and sometimes long-term, BUT the grasses are never "giving up the land to natural succession". The grasses become a permanent fixture and then do not allow the shrub, alder, conifer habitat succession!!
David has presented some new technologies to prevent erosion over the short term and allow planting or natural recruitment of the "native early successional plants".
Check out the power point presentation(s) on "Rough and Loose" and "Battle Lake Site" provided by David Polster.