A national-scale IDF-based design storm hyetograph inventory: Applying the Catchment2Storm tool in Greece

INTRODUCTION

We present an automated Python-based tool called Catchment2Storm that generates design storm hyetographs directly from watershed shapefiles, using the official Greek gridded IDF parameters ("ombrian parameters") provided by the Ministry of Environment. We apply it to an indicative watershed, and at the national scale (~11,000 sub-catchments), providing an inventory of design storms.

METHODS

The tool overlays a user-defined catchment shapefile onto the national IDF grid, which is publicly available from the Greek Ministry of Environment. Then, the IDF grid cells that intersect the user’s catchment are identified. For each intersected polygon (sub-catchment), the script calculates its area and relative contribution to the total catchment, extracting the corresponding IDF parameters. Intensity and Precipitation depth are computed for each sub-area over a user-selected storm duration, return period, and time interval. The storm is reduced spatially using the Area-Reduction-Coefficient Phi, and is temporally rearranged using the Alternating Block Method (ABM), resulting in a ready-to-use hyetograph.

RESULTS

The output includes a hyetograph plot, Excel summaries, and rainfall input tables formatted for direct use for HEC-HMS and HEC-RAS. We showcase how this tool can be also used for multiple catchments: We have applied it to all Greek sub-catchments (N=10,773), using a batch-run approach in Python, which also summarizes key metrics for different hyetographs.

CONCLUSIONS

The developed Catchment2Storm tool has been developed in Python, and we are considering its commercial use. All materials are stored in a private Github repository ( https://github.com/Alamanos11/Catchment2Storm ), including step-by-step guidance on running the tool, sigle-or-multiple catchments, summarizing key results’ metrics, and mapping them, even in the case of missing values.

Catchment2Storm streamlines the process of generating design storms by automating geospatial analysis and storm synthesis directly from national IDF data, at any catchment or scale, providing accurate, model-ready hyetographs in seconds.