Abstract
To develop intensity-duration-frequency (IDF) curves, it is necessary to calculate annual maximum rainfall intensities for different durations. Traditionally, these intensities have been calculated from the analysis of traces recorded by rain gauges on pluviograph strip charts (PSCs). For many years, these charts have been recorded and analyzed by the personnel who operate and maintain the pluviograph gauges, thus the reliability of the observational analysis depends exclusively on the professional experience of the person performing the analysis. Traditionally, the analyzed PSCs are physically stored in data repository centers. After storing rainfall data on aging paper for many years, the risk of losing rainfall records is very high. Therefore, the conversion of PSC records to digital format is crucial to preserve and improve the historical instrumental data base of these records. We conducted the first “Data Rescue Initiative” (DRI) for central Chile using a pluviograph strip charts reader (PSCR), a tool that uses a scanner-type device combined with digital image processing techniques to estimate maximum rainfall intensities for different durations for each paper band (>80,000 paper bands). On the paper bands, common irregularities associated with excess ink, annotations, or blemishes can affect the scanning process; this system was designed with a semi-automatic module that allows users to edit the detected trace to improve the recognition of the data from each PSC. The PSCR’s semi-automatic characteristics were designed to read many PSCs in a short period of time. The tool also allows for the calculation of rainfall intensities in durations ranging between 15 min to 1 h. This capability improves the value of the data for water infrastructure design, since intense storms of shorter duration often have greater impacts than longer but less intense storms. In this study, the validation of the PSCR against records obtained from observational analysis showed no significant differences between maximum rainfall intensities for durations of 1 h, 6 h, and 24 h.
Highlights
Having considered previous international work, we developed a semi-automatic pluviograph strip charts reader (PSCR) to perform a rainfall data rescue initiative (DRI) for central Chile
The DRI described here allowed us to create the first database of rainfall amounts and maximum rainfall intensities for central Chile
The collection and the pre-selection of PSC are intensive activities that can take a significant amount of time and resources within a DRI
Summary
The recorded data have high temporal resolution when compared to pluviometer rain gauges, which only measure. Pluviograph rain gauges are devices that continuously measure rainfall intensity. The recorded data have high temporal resolution when compared to pluviometer rain gauges, which only measure daily. This device collects rainfall in aa bucket used in Chile is the float-based pluviograph (see Figure 1a) This device collects rainfall in bucket containing a lightweight float; as the water level in the container rises, the elevation of the float drives containing a lightweight float; as the water level in the container rises, the elevation of the float drives the movement of a pen over a band of paper as it slowly rotates around a cylinder
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