Analysis codes to conduct Quantile-Kendall trend analysis across flow duration curve of streamflow in urbanizing watersheds across U.S.

These are a set of codes to accompany the Water Resources Research submission by Bhaskar et al.

The following codes are run in this order:
1. GAGESII_subset_urbanizing.R

This codes identifies urbanizing watersheds and associated peak 20-year periods of urbanization from GAGES-II based on the criteria of:
1. Drainage area < 200 km2
2. 20 years of completely gap-free daily flow
3. Unaffected by regulation or diversion
4. Housing density increased by > 40% during period of analysis
5. Housing density > 200 housing units/km2 at end of analysis period
6. Imperviousness > 20% in 2012

2. selection_of_reference_gages.R

This code picks a reference gage from GAGES-II reference gages for each urbanizing gage based on the minimization of a function with 4 criteria: distance, similar drainage area, similar precipitation, and similar geology.

3. compare_urbanizing_gage_trends.R

This code calculates quantile-Kendall trend slopes for just the urbanizing gages.

4. gages_reference_vs_urbanizing.R

This code calculates quantile-Kendall trend slopes for the urbanizing and reference gages, subtracts them, creates plots, and has regression analysis. This code uses gages_urbanizing_2019-11-27_Plotting.groups.csv to group urbanizing gages into regional groups for plotting purposes.