Riparian Characteristics - USEPA/ATtILA2 GitHub Wiki

Introduction

Riparian zones, i.e., the areas adjacent to streams and associated waterbodies, provide critical habitat areas and play an important role in determining or preserving surface water quality. While all of the land area within a watershed may contribute pollutants via runoff, the effect of more distant (from stream) areas may be mitigated along the transport path. However, there is little or no mitigation of nutrient or soil runoff from stream side areas. Thus these buffer areas along streams may have a greater impact upon water quality. Conversely, conservation of riparian buffers may help to preserve good water quality.

The Riparian Characteristics toolset consists of the follow metric tools:

  • Floodplain Land Cover Proportions Calculates the percentage of floodplain area within a reporting unit classified as selected land cover classes and creates an output table.

  • Riparian Land Cover Proportions is similar to the Land Cover Proportions metric in the Landscape Characteristics toolset except that the results are calculated only for the buffer area around streams instead of over the whole reporting unit. Input features may be lines or polygons or both. Adjacency is determined by a buffer distance specified by the user. Additionally, reporting unit boundaries can be selected to act as an absolute barrier when creating buffer areas or ignored. If boundaries are enforced, buffer areas for features outside of the reporting unit will stop at the reporting unit boundary, elsewise buffer areas for features outside of the reporting unit are allowed inside the reporting unit.

  • Sample Point Land Cover Proportions Calculates the percentages of selected land cover types within the area adjacent to input point features in each reporting unit and creates an output table. Adjacency is determined by a buffer distance specified by the user. Additionally, reporting unit boundaries can be selected to act as an absolute barrier when creating buffer areas or ignored. If boundaries are enforced, buffer areas for features outside of the reporting unit will stop at the reporting unit boundary, elsewise buffer areas for features outside of the reporting unit are allowed inside the reporting unit.

  • Stream Density Metrics Calculates density metrics based on input vector line dataset(s) for each reporting unit polygon and creates an output table. Default metrics include area of the reporting unit (km²), total length (km) and line density (km/km²) within the reporting unit. In addition to the default metrics, length and density metrics can be calculated by stream order. Stream order is designated based on values in a specified field in the Stream feature layer.

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