Topic: Author: Jimmy Mills Date: Saturday - October 19, 2013 From: Dallas, TX
QUESTION: After consulting with several geological engineers and the city of Dallas engineers - we know that our severe erosion problem can only be fixed by building a 35' foot high gabion wall about 150' in width. Due to the expense, it may be several years before the construction takes place. Currently the slope to the creek is nearly nonexistent - but rather a near vertical drop off. We've lost 4 large trees within the last 2 years due to loss of soil around the roots, and an arborologist has given a dire prediction of losing an additional 5 - 7 trees within the next few years. We are desperately trying to hang on to as much soil as possible until the walls can be put in. We built a 2' retaining wall located 4' before the drop off. Due to the instability of that area - we were instructed not to due any digging. Plus it's not a stable area to do a lot of gardening type work. Last spring we attempted to introduce inland sea oats, which seemed to do well until June - and the heat/sun seemed to kill them off. We are in need of a year round plant for that area (some is in the sun for 6 hours per day, some in in the shade) that we can simply spread by seed as we cannot till or dig. We've been informed the area is too small and unstable for erosion control blankets - so one issue is how to keep the seed on the land without it washing down into the creek. We've contacted almost every agency in Texas that deals with erosion and each one of them has been at a loss other than to get the gabion walls in as quickly as possible. But we are on the city's timeline. Thank you in advance for your recommendations
That sounds like quite an undertaking, and the engineering aspects of the project are far removed from Mr. Smarty Plants area of expertise. But since you mentioned Inland Sea Oats (Chasmanthium latifolium (Inland sea oats), lets talk some more about grasses. We often suggest using grasses for erosion control since their fibrous root systems are able to hold on to soil particles quite effectively.
The first bit of information is that there are cool season grasses and warm season grasses. Warm season grasses germinate in the spring and, since they are heat and drought tolerant, are generally green throughout the spring and summer. They begin turning brown in the fall and remain so throughout the winter. Cool season grasses germinate in the fall and are green and growing throughout the winter and spring, but die back in the heat of summer. What category do you think Inland Sea Oats is in?
So if you are wanting some type of grass cover throughout the year, you might consider a rotation of warm season and cool season grasses to help stabilize the soil. This previous answer deals with grasses in East Texas and has several examples of warm and cool season grasses.( Note that Inland Sea Oats should be in the cool season category.)