Utah Statewide RVD

A riparian vegetation departure was conducted for all valley bottoms of the state. We did this using the Riparian Vegetation Departure (RVD) tool in ArcGIS. RVD uses LANDFIRE EVT and BpS data, to estimate riparian vegetation change within the valley bottom since Euro-American settlement at a reach level (500 m segments). The BpS layer represents the vegetation that may have been dominant on the landscape prior to Euro-American settlement and is based on both the current biophysical environment and an approximation of the historical disturbance regime. We used the BpS layer to represent the reference (pre-settlement) vegetation condition and the EVT layer was used to represent the current (2012) vegetation condition. The vegetation condition assessment was accomplished by coding native riparian vegetation as a 1 and non-native riparian and upland classes as a 0. In addition, within large rivers, the open water class was coded as NoData and outside of large rivers open water was coded as a 1. This coding was determined through test runs of the assessment that found that if all open water was classified as a 1 it overestimated the riparian condition along large rivers and if all open water was classified as NoData it underestimated the riparian condition along smaller rivers. The following equation was used to calculate a dimensionless ratio: (mean EVT vegetation value)/(mean BpS vegetation value). The lower the value (closer to 0) the more degraded the riparian vegetation condition was compared to the pre-settlement condition and the higher the values (Closer to 1) indicate a small departure from pre-settlement condition. In rare cases values larger than 1 were identified and indicating areas that have increased in native riparian vegetation since settlement.