Which of the following would not affect the determination of slope gradient?

The determination of slope gradient is primarily influenced by quantitative measurements and geometric relationships. The vertical rise and horizontal run are crucial elements; they directly define how steep a slope is. The angle of the slope is also essential, as slope gradient is essentially a function of this angle. The method of measurement pertains to the techniques used to quantify the slope, which can also impact the accuracy of the slope calculation.

In contrast, surrounding vegetation does not technically impact the actual measurement or calculation of the slope gradient itself. While vegetation may affect stability, water runoff, and other environmental factors related to slopes, it does not alter the fundamental geometric relationship or the calculations needed to determine the slope gradient. Thus, it would not be a factor in the direct measurements of slope or angle, making it the choice that does not influence the determination of slope gradient.