The pattern is tree-like when viewed from above. The intersection of streams is a confluence and is most likely an acute angle unless some structural feature interrupts the pattern. This type of drainage is common in the Texas Hill Country. At this point the river can no longer meander but is fixed or entrenched. Walls of the canyon are a function of the hardness of different layers of strata.
Soft layers tend to form slopes and harder layers form cliffs.
This forms an ox-bow lake which gradually fills with sediment resulting in a meander scar. These features are very common along the Mississippi River. The lower portion of the Rio Grande around Brownsville, TX also has numerous meander scars. A fold or fault may create a difference in outcrops. The harder rock is at the top and the softer below.