The importance of preventing damage from pluvial flooding has been increasing under global climate change. The discovery of premonitory symptoms of pluvial flooding enables effective evacuation and inundation prevention activities. However, apparatuses that automatically detect this in real time are not widespread. There are difficulties in the cost of installing them and the agreements made by the parties concerned, especially in cities. To solve this problem, we devised an apparatus to be installed inside a catch basin that detects its water level. The water level in the catch basin may indicate a sign of pluvial flooding, and the number of people involved in operating the catch basin is smaller than that of facilities on the ground. In order to reduce the cost of installation and operation, we adopted Low Power Wide Area (LPWA), which is a communication method that enables wireless transmission of detected information over long distances for a long time using batteries. So far, for catch basins, a wireless transmission experiment was conducted using LoRa, which is part of LPWA. However, Sigfox, which uses the same frequency as LoRa but has a different wireless system, has not been verified. In this study, the reliability of wireless communication was assessed by apparatuses using LoRa and Sigfox side by side in each catch basin in two places in a densely populated city. The number of experiment days and transmissions differed depending on the apparatus, with the number of days ranging from 97–151 and the number of transmissions from 2328–3748. The reliability in the experiment ranged from 99.97–99.53%. The experimental results showed that wireless transmission was possible with high reliability using either the LoRa or Sigfox system from inside these catch basins. This study expands the options for communication infrastructure that can be used for apparatuses that detect premonitory symptoms of pluvial flooding. This will enable a reduction in installation costs and will expand the range of areas of potential installation.

1. [1] W. Kobayashi and M. Ohara, “Flood control information system for securing evacuation and preventing flooding: development and application to the west area of Yokohama Station,” J. of Japan Society of Civil Engineers, Ser. F5 (Professional Practices in Civil Engineering), Vol.76, No.1, pp. 84-97, 2020 (in Japanese).
2. [2] T. Kogure, “Natural disaster measures on Tokyo Metro,” J. Disaster Res., Vol.11, No.2, pp. 289-297, 2016.
3. [3] J. Kanai and S. Nakano, “Evacuation behavior of facilities for the elderly in the heavy rain of July 2018,” J. Disaster Res., Vol.14, No.6, pp. 922-935, 2019.
4. [4] W. Kobayashi and M. Ohara, “Real-time monitoring of flood inundation in urban area using LPWA,” J. of Japan Society of Civil Engineers, Ser. F3 (Civil Engineering Informatics), Vol.75, No.1, pp. 36-47, 2019 (in Japanese).
5. [5] W. Kobayashi and K. Fujimoto, “Monitoring technologies for river management,” J. of The Society of Instrument and Control Engineers, Vol.55, No.2, pp. 151-156, 2016 (in Japanese).
6. [6] S. Lee, Y. Shibuo, and H. Furumai, “Change of water level and electric conductivity using monitoring data at combined sewer pipes in Tsurumi river basin,” J. of Japan Society of Civil Engineers, Ser. G (Environmental Research), Vol.75, No.2, pp. 55-64, 2019 (in Japanese).
7. [7] M. Murase, M. Takeda, T. Yagami, T. Takahashi, K. Oya, and R. Yamauchi, “Examination of countermeasures of inundation due to heavy rain by numerical analysis and observation of the sewer water level in Kasugai city,” J. of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), Vol.75, No.2, pp. I_1267-I_1272, 2020 (in Japanese).
8. [8] Sewerage Department of Water and Disaster Management Bureau in Ministry of Land, Infrastructure, Transport and Tourism in Japan, “Guide for promoting observation of water level in sewer pipes (draft),” 2017 (in Japanese).
9. [9] Sewerage Department of Water and Disaster Management Bureau in Ministry of Land, Infrastructure, Transport and Tourism in Japan, “Technical data (draft) related to the water level publicity sewerage system,” 2016 (in Japanese).
10. [10] International Telecommunication Union Radiocommunication Sector, “Propagation data and prediction methods for the planning of short-range outdoor radiocommunication systems and radio local area networks in the frequency range 300 MHz to 100 GHz,” ITU-R Recommendations, No.P.1411-9, pp. 15-21, 2017.
11. [11] Semtech Corporation, “AN1200.22: LoRa™ modulation basics,” Revision 2, https://www.semtech.com/uploads/documents/an1200.22.pdf [accessed January 3, 2019]
12. [12] Sigfox, https://www.sigfox.com/en/what-sigfox/technology [accessed September 10, 2020]
13. [13] B. Vejlgaard, M. Lauridsen, H. Nguyen, I. Z. Kovács, P. Mogensen, and M. Sorensen, “Coverage and capacity analysis of Sigfox, LoRa, GPRS, and NB-IoT,” IEEE 85th Vehicular Technology Conf. (VTC Spring), pp. 1-5, 2017.
14. [14] M. Lauridsen, H. Nguyen, B. Vejlgaard, I. Z. Kovács, P. Mogensen, and M. Sorensen, “Coverage comparison of GPRS, NB-IoT, LoRa, and SigFox in a 7800 km² area,” IEEE 85th Vehicular Technology Conf. (VTC Spring), pp. 1-5, 2017.
15. [15] Ministry of Land, Infrastructure, Transport and Tourism in Japan, “Flood report 2004,” https://www.mlit.go.jp/river/pamphlet_jirei/bousai/saigai/kiroku/suigai2004/kanto.html [accessed January 3, 2019]
16. [16] Kyocera Communication Systems, “What is Sigfox?,” https://en.kccs-iot.jp/service/ [accessed November 20, 2020]
17. [17] International Telecommunication Union Radiocommunication Sector, “Specific attenuation model for rain for use in prediction methods,” ITU-R Recommendation, No.P.838-3, 2019.
18. [18] Association of Radio Industries and Businesses, “920 MHz-Band Telemeter, Telecontrol and Data Transmission Radio Equipment,” ARIB STD-T108, https://www.arib.or.jp/english/std_tr/telecommunications/desc/std-t108.html [accessed June 13, 2020]