Trees key vs. slides
The news story " McArdle Roadway fix could take a while " (Jan. 13 and TribLIVE.com) lacked answers. The landslides along this portion of McArdle, especially this most damaging slide, were in fact caused by cutting trees under the overlook during late summer 2010, just before the G-20 summit.
The trees growing there were thriving and holding the steep hillside in place for decades. Actually, the trees' living roots were holding the very shallow soil in place. So why did the hillside not slide in late 2010• Because the roots were still living and stabilizing the slope. Now the roots are dying or nearly dead. As roots decompose, water fills the voids. This further undermines the soil above.
The roots grew through the shallow soil and into cracks in the bedrock to "anchor" the soil and keep the hillside stable.
This destruction of nature's balance, no matter how minor (as compared to the Kilbuck Wal-Mart site catastrophe in 2006), should be a wake-up call to municipalities trying to work against nature, whether by building into or cutting trees off hillsides.
The "Band-Aid" that the city wants to use will never solve the problem. Only replanting the slope with deep-rooted trees will. That could cost tens of thousands of dollars and complete stabilization will take years, if not a decade.
Steep hillsides should not be disturbed, but held in place by the trees that God intended these slopes to be protected with.
The writer is a soil scientist with Agronomics Soil Consulting in Carnegie.