Measuring reach-scale geomorphic heterogeneity by using landscape indices: implications for river management

An accurate understanding of the geomorphic heterogeneity of a river is critical for river management and protection. In this paper, landscape indices, which are widely used in landscape ecology for spatial heterogeneity evaluation, were used to quantify the geomorphic heterogeneity at the reach scale and to identify the important geomorphic features for river management. Eight types of geomorphic patches were extracted from remotely sensed images, and then landscape indices characterizing the geomorphic structure and pattern of a river reach were calculated. Geomorphic structures were determined by measuring the dominance, patch size, and patch shape of geomorphic-patch types. And the geomorphic pattern was measured by using the indices reflecting the spatial configuration of geomorphic patches, hydrological connectivity, and the relative acreage of a geomorphic patch type to the river water surface. Results from the upper and lower Jingjiang reach of middle Yangtze of China showed that these indices can well present the differences in geomorphic structures and patterns within the reach. Based on these quantitative measurements, a set of criteria was established to identify the geomorphic components that are critical, important, or negative for the river-floodplain system. Management strategies targeted to these varied geomorphic components were then formulated and would fundamentally conform to the geomorphic heterogeneity of the river-floodplain system.