Geospatial Analyses of Drought Impact and Severity in North Dakota, USA Using Remote Sensing and GIS

An analysis of spatial and temporal variance of drought impact may offer an unbiased glimpse into factors that may dictate drought severity. This study sought to assess spatio-temporal drought impact factors at county level for the entire state of North Dakota, USA. Remote sensing techniques were used to analyze the drought impact on active vegetation. Drought intensity classification based on weekly percentage of areal coverage values published by U.S drought monitoring program at National Drought Mitigation Centre were used to assess drought severity. This classification schema is based on objective analysis of (a) Palmer Drought Index, (b) CPC Soil Moisture Percentiles, (c) USGS weekly stream flow percentiles, (d) Standardized Precipitation Index (SPI), (e) objective short and long-term drought indicator blends percentiles, and (f) objective local input. County-by-county weekly common drought severity and coverage values are non-dimensional indices called Drought Severity and Coverage Index and were calculated from the weekly percentage of areal coverage values for a period of about nine years (January 2000 to April 2009) to determine the drought severity. A drought severity spatial variability map was thereafter generated from the drought impact values. Drought events were first categorized into classes based on weekly common drought severity values to analyze drought frequency. The number of occurrence of drought events were then determined for each county based on derived classes. The drought frequency analyses showed clear demarcation of counties being more and less susceptible to certain droughts in North Dakota. Normalized Difference Vegetation Index (NDVI) raster datasets were derived from Landsat 7 ETM+ satellite imagery for the southwest region of the state. This region displayed a significantly impacted drought region. NDVI results were compared to drought severity values for affected counties. From this study we found a county-by-county drought study may be useful in implementing drought mitigation plans, and managing available water resources, and offering Best Management Practices (BMPs) for agricultural activities.