Influences of different surveying and mapping methods on fractal characteristics of gully-head shoulder lines

Abstract

2016): Influences of different surveying and mapping methods on fractal characteristics of gully-head shoulder lines, Physical Geography, ABSTRACT Accurate quantification of gully shoulder lines (gully borderlines) will help better understand gully formation and evolution. Surveying and mapping are the most important ways to obtain precise morphology. To evaluate the influences of different steps of surveying and of curvefitting methods of mapping on the morphology of the shoulder line characterized by fractal dimensions, 13 shoulder lines at gully heads were surveyed using a total station and then mapped with different methods of curve fitting, with the fractal dimensions calculated by maps compared with those measured in the field. Fractal dimensions by field measurement ranged from 1.185 to 1.456. Compared with field measurements, the average absolute errors of polygonal line, quadratic B-spline, and arc-fitting methods are 0.045, 0.040, and 0.046, respectively; the average relative errors are 3.48, 3.13, and 3.59%. Therefore, the quadratic B-spline method has a higher accuracy. The standard error of the fractal dimension tends to be larger as average step length increases. The error is ~5% when the step length is 0.7 m, which is advisable for field surveying. This study will help promote the efficiency of field surveying and mapping, and thus promote the accuracy and credibility of gully morphology.

Geomorphic natural hazard on loess terrain: expansion on the gully sidewall

“…The gully shoulder line is always located in the most active part of a gully and its dynamics reflect the development of the gully (Liu et al 2016). The retreat rate of the gully shoulder line mirrors not only the outward appearance of the developing gully, but also the internal mechanisms of gully development (Zhang et al 2012).…”

“…Gully sidewall extension is an important process in gully development (Blong et al 1982), and its dynamic nature can be assessed from changes in the gully shoulder line (Liu et al 2016). The gully shoulder line is the line that intersects the gentle slope and gully sidewall (Fig.…”

Population Characteristics of Loess Gully System in the Loess Plateau of China

“…The loess shoulder line was extracted at first. The shoulder line (Figure 1) is the boundary between positive (excavated or interfluves) and negative (valley) terrains, which divides the area between the permanent gully (bank gully and valley gully) and ephemeral gully [37][38][39][40][41]. Then, the bank gully and valley gully could be extracted by our proposed method [33] based on hydrological analysis; morphological features were also considered.…”

“…Thus, the shoulder line was extracted. Among the proposed methods [37][38][39][40][41], the P-N terrain segmentation algorithm [37] was selected because of its satisfactory performance on 5 m DEMs, both in accuracy and continuity. Then, the hillslope ephemeral gully was delineated using extracted shoulder line as a reference line.…”