The Technical Guide “Technical Recommendations for Local Flood Studies” (published by ACA in March 2003) has become one of the primary guides for hydrological characterization studies on watercourses within Catalonia’s Internal River Basins, mainly utilizing the Témez Rational Method.
This systematic methodology involves repetitive assumptions of certain calculation hypotheses and methodological application in each new study, sometimes with varying criteria.
Additionally, the Catalan Water Agency (ACA) has been conducting a significant number of flood studies with specific hydrological modeling to obtain flow rates and flood hydrographs for subsequent use.
The need has arisen to develop a standardized flood flow coverage, integrating the results of ACA’s previous studies with a systematic and justified application of the Témez Rational Method to other watercourses within the hydrographic network of the Catalonia River Basin District.
This aims to establish a single reference for studies and interventions impacting the Public Hydraulic Domain and its Police Zone, for both public and private promoters and ACA as the basin authority.
In the initial phase, all available data was compiled, primarily from ACA, including flood flow data and information required for the Rational Method calculations. The collated data was analyzed to identify the most representative information for the region’s hydrological characteristics. The data sources used in the Rational Method calculations were:
Geological Map of Catalonia at 1:250,000 scale
Land Cover Map of Catalonia (MCSC v4 from 2009)
Rainfall Data from the Meteorological Service of Catalonia (2021)
ICGC 15×15 Digital Terrain Model
All data was processed in raster format to allow for generalized and automated use, requiring the development of auxiliary codes in some cases. Using GIS tools and based on accumulated area (Flow Accumulation, treated as a calculation weight), these parameters were accumulated across the DCFC network.
The complete hydrographic network coverage (1:50,000 scale vector format) from ACA was corrected to align watercourse paths with the ICGC’s Topographic Base and 1:5,000 Orthoimages, particularly in urban areas. In specific cases, these path adjustments were necessary to match real watercourse paths. From this corrected coverage, calculation points were determined every 50 meters for mass application of the Rational Method, resulting in a total of 702,441 points.
A critical parameter, the Témez Number (I, II, or III), was determined semi-automatically, starting from a minimum urbanization rate (50%) and adjusting for continuity and hydrological coherence. Each network point’s data was stored in a CSV file and interpreted by a Python code developed for this project, capable of processing unit-structured data and executing the Rational Method for each point.
Additionally, ACA’s flow sectioning data (from more detailed hydrological models than the Rational Method) was incorporated into the coverage of the Rational Method’s mass application results. Hydrological criteria were established to harmonize the two data sets.
In addition to the standardized flow coverage and the Python code developed in this project, individual calculation point reports were automatically generated.
To manage this extensive task efficiently, codes were configured to allow parallel report generation across multiple cloud servers.
This enabled a synthesis of flow rates and other calculation parameters, providing a unified reference framework for future flood studies and ensuring consistency in initial parameters (flow rates and hydrographs derived from calculation parameters) for flood studies within the Catalonia River Basin District.
This information is now publicly available on ACA’s viewer.
Length of Studied Courses: 32,325 km
Number of Calculation Points: 702,441
Use of GIS and SQL Queries for Mass Data Processing
Creation of Python Code for the Rational Method Calculations
Client: Agència Catalana de l’Aigua
Year: 2020-2021
Distrito Cuenca Fluvial de Cataluña (DCFC)
