Brushy Creek rises three miles northwest of Leander in southwestern Williamson County and flows east for sixty-nine miles, through southern Williamson County and southwestern Milam County, to its mouth on the San Gabriel River, five miles north of Rockdale. The stream is intermittent in its upper reaches. It was named Arroyo de las Ánimas Benditas (Creek of the Blessed Souls) by explorers Louis Juchereau de St. Denis and Domingo Ramón in 1716 and was known by variations of that name throughout the Spanish colonial period. It was the site of several of the earliest communities in the county. The battle of Brushy Creek occurred near its banks in 1839. The banks of the stream are heavily wooded for much of its length with mesquite and hardwood trees, and the creek flows through nearly level to gently rolling terrain surfaced by clayey and loamy soils used predominantly for agriculture.
Brushy Creek Soil
As mentioned above this creek runs through mostly loam soil. So what is loam soil? Loam soil is composed of almost equal amounts of sand and silt with a little less clay. A good ratio is 40 percent each of sand and silt, and 20 percent of clay. Among loam's three components—sand, silt, and clay—the sand particles are the largest. Sand does not hold on to moisture, but it provides good aeration and drainage.
On the opposite end, clay particles are much smaller and easily compacted. That makes clay a great material for building bricks but not so great for allowing water, air, and plant roots through. However, clay tends to be higher in nutrients than the other soil components.
Silt is the medium-size particle, with better moisture retention than sand but fewer nutrients than clay. Silt helps clay and sand mix together more readily, like tempering chocolate. In addition to providing nutrients and water effectively, loam has a loose and crumbly texture. This is referred to as friable. Loose soil provides room for air to mix into the soil, which is also necessary for optimal plant growth. The friable nature of loam also makes it easy for roots to grow and reach more nutrients and water.
Brushy Creek Erosion
Bank scour - Bank scour is the direct removal of bank materials by the physical action of flowing water and the sediment that it carries. Water also increases and scour may occur. Increases in flow speed can be the result of natural and/or human induced processes. Undercutting of the bank toe is an obvious sign of scour processes. Effective strategies for combating scour are generally aimed at reducing flow speed through revegetation and in some cases through strategic bank or channel works.
Mass failure - Mass failure describes the various mechanisms of bank erosion that result in sections of the bank sliding or toppling into the stream. Mass failure is sometimes described as collapse or slumping. Bare and near-vertical banks or areas of slumped bank materials are obvious signs of these processes. The causes of these types of failures are often difficult to determine but can include natural and/or human factors. Slumping as a result of saturation after flooding are common examples of mass failure.
In order to log this Earth Cache, please answer the questions below and send me an email with the answers.
1. What is the color of the soil on the banks of Brushy Creek at this location and what type of soil does it seem to be?
2. Please explain how bank erosion has effected the formation of Brushy Creek.
3. Does this area suffer from Bank Scour?
4. Do you see evidence of any Mass Failure here?
5. As proof that you have visited this location, please take a picture of yourself here with Brushy Creek in the background. We would love to see visitors here with their happy faces or safety masks while enjoying this earthcache.