Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student Jacob Sanua makes this connection here…

The news article “Using moving cars to measure rainfall” was reported by the European Geosciences Union on November 23rd, 2013. This research is in the hydrology domain of WRE, and focuses on the occurrence and measurement of rainfall over large areas. The article reports on lab trials of a system designed to measure rainfall by correlating rainfall with the speed of windshield wipers on GPS-equippted cars. The premise is that the harder the rain falls, the faster the wipers wipe, either controlled manually or by an optical sensor. The program, called “RainCars” aims to provide a much higher network density of rainfall measurements than is currently offered by existing rain gauges. So far, researchers have begun controlled lab tests to determine the correlation between wiper speed and rain intensity, and field trials with volunteers such as taxis and car companies are in the works. Based on my engineering education, it seems to me that the accuracy of the method would turn out to be questionable, but the authors do refer to a modeling study of the technique published by two of the team members, U.Haberlandt and M.Sester, that found that many data points of less accurate rain measurement give more reliable areal rainfall readings than a sparse spattering of highly accurate rain gauges. The article does not mention how successful the researchers were in their laboratory tests, but that information is contained in the published paper that this article is reporting on.

Accurate areal rain measurement is very important in predicting and mitigating flooding. Bringing this issue into a broader context, this WRE article falls within societal and economic areas. Rainfall estimation is important to predict flooding, which impacts society(lives and social relationships) as well as the economy(property, possessions, values). Though this method of measuring rainfall with cars is highly experimental, if found useful it could, partnered with other technologies like radar, increase the accuracy of measuring rainfall and directly impact the accuracy of flood modeling. V.E Dainiel, R. J. G. M. Florax, and P. Rietveld report that the occurrence of such disasters is “associated with substantial costs, both in the form of human and material losses or disruption of economic activity”. Radar rainfall estimates alone are not accurate enough for hydrologic modeling, they need to be calibrated against ground measurements (S. Thorndahl, J. E. Nielsen, M. R. Rasmussen, 2014). If rainfall estimates are not accurate, flood modeling may be unpredictable and increased human and economic loss incurred due to unpreparedness or misdesign of flood structures.

Car being tested under a rain simulator

Car being tested under a rain simulator

Drawing of rain simulator setup

Drawing of rain simulator setup

References:

Rabiei, E., Haberlandt, U., Sester, M., and Fitzner, D.: Rainfall estimation using moving cars as rain gauges – laboratory experiments, Hydrol. Earth Syst. Sci., 17, 4701-4712, doi:10.5194/hess-17-4701-2013, 2013.

U. Haberlandt and M. Sester: Areal rainfall estimation using moving cars as rain gauges – a modelling study, Hydrol. Earth Syst. Sci., 14, 1139-1151, 2010.

Vanessa E. Daniel, Raymond J.G.M. Florax, Piet Rietveld, Flooding risk and housing values: An economic assessment of environmental hazard, Ecological Economics, Volume 69, Issue 2, 15 December 2009, Pages 355-365, ISSN 0921-8009, http://dx.doi.org/10.1016/j.ecolecon.2009.08.018. (http://www.sciencedirect.com/science/article/pii/S092180090900322X)

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