Quantifying contour rip line error in altered landscapes using high resolution digital elevation models

Contour ripping is a well-demonstrated surface preparation technique used to control the overland flow of water and prevent soil erosion, while providing storage and increasing infiltration. Although the importance of contour ripping is well discussed in literature, few methods have been developed to automatically analyse ripped landforms to accurately quantify ripping direction without the need for manual delineation. Identifying the degree of contour error, and its interaction with other landscape features, is an important step in understanding the movement of surface water in modified landscapes. At present, there are no available tools to determine ripping direction in altered landscapes. We present a new workflow that utilises high resolution Digital Elevation Models (DEMs), and common Geographic Information System (GIS) techniques to estimate rip line direction, evaluate the reliability of that estimate, quantify deviation from the generalised topographical contour (rip line error), and derive a functional metric (furrow slope) that reflects the severity of off-contour ripping. This workflow provides an autonomous alternative to manual delineation of contour ripping orientation, without reliance on any 3rd party software or proprietary engine. The workflow proved to be substantially faster than manual delineation, and the results were of similar or better accuracy than existing attempts in literature. Through this approach, new opportunities for land management are made available by providing data critical for surface water modelling and landform stability risk assessments.