My writeup for the technical assessment is here: JonathanFrame_C2S_technical_challenge.pdf
Well actually the return period analysis was done using this public Matlab code: https://www.mathworks.com/matlabcentral/fileexchange/22628-log-pearson-flood-flow-frequency-using-usgs-17b
Once those return periods were calculated, here is my code for analysis of return periods: analysis_code_c2s_tulsa_2019.ipynb