Xiaoxiang Guan

• GFZ Helmholtz Centre for Geosciences

• Compound hydrologic extremes & multi-hazards
• Flood hazard and risk assessment
• Unprecedented floods: trends, characteristics, and modelling
• AI-enhanced hydrological modelling

• 1. Compound Flooding: Assessing the Risk of Compound Pluvial and River Flooding

Advance compound flood hazard assessment by integrating a novel modeling frameworkspanning sub-daily stochastic climate generation, rainfall temporal disaggregation, hydrological simulation (mHM), hydrodynamic inundation modeling (RIM2D), and flood impact estimation (FLEMO)to quantify the amplification of compound pluvial and fluvial flood risks in the Ahr Valley, Germany.

• 2. KAHR: Climate Adaptation, Floods and Resilience

Scientific support of the reconstruction processes following the flood disaster in Rhineland-Palatinate and North Rhine-Westphalia Evaluate the severity of the rainfall event that caused the record-breaking flood in the Ahr area in July 2021 using the cross-scale weather extremity index (xWEI), which quantifies weather extremes across durations and spatial scales.

• 3. BMBF ClimXtreme: Teilprojekt C5 FLOOD Linking extreme, large-scale river floods and their impact in Central Europe to climate and weather mechanisms.

Quantify how anthropogenic climate change influenced the July 2021 Ahr Valley flood by comparing the likelihood of extreme precipitation and flood peaks between a present-day and a pre-industrial climate scenario. Develop a Freva plugin for quick flood inundation assessment of large-scale riverine floods in Germany and neighboring basins.

• 1. 12th International Workshop on Statistical Hydrology (STAHY2022), Sardinia, Italy, 17th-20th September 2022 Poster presentation on Multisite temporal rainfall disaggregation using methods of fragments conditioned on circulation patterns

• 2. XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG), Berlin, 2023 Oral presentation on precipitation event extremity evaluation by a cross-scale weather extremity index across Germany

• 3. 2025 EGU General Assembly, Vienna, 27th April - 3rd May 2025 Oral presentation on Hazard assessment of compound pluvial and fluvial (CPFF) flooding: a case study in the Ahr valley

Journal articles 

• Guan, X., Merz, B., Nguyen, V.D, Han, L., Apel, H., Khosh Bin Ghomash, S. Guntu, R.K., Kreibich, H., Vorogushyn, S. 2026. Amplification of flood hazard and damage by compounding pluvial and fluvial flooding. Earth’s Future. DOI:10.1029/2025EF007048 (accepted for publication).
• Xie, M., Zhang, J., Bao, Z., Zhang, L., Duan, Z., Wang, G., Liu, C., Yuan, F. and Guan, X. 2026. Improving evapotranspiration estimation by integrating process-based biophysical variables into a deep learning approach. Journal of Hydrology: Regional Studies, 63, 103114. doi: https://doi.org/10.1016/j.ejrh.2026.103114.
• Guan, X., Nguyen, V.D, Voit, P., Merz, B., Heistermann, M. and Vorogushyn, S. 2025. The ability of a stochastic regional weather generator to reproduce heavy-precipitation events across scales. Nat. Hazards Earth Syst. Sci., 25(9), 3075-3086. doi: https://doi.org/10.5194/nhess-25-3075-2025.
• Kreibich, H., Murugesu, S., Amir, A., Nans, A., Hafzullah, A., Berit, A., Karsten, A.-N., Cynthia, V.-C., Christophe, C., Mariana, M.d.B., Giuliano, D.B., C., F.D., Keirnan, F., Wouter, K., Tobias, K., Junguo, L., Elena, M., Hilary, M., Mario, M.E., Alberto, M., F., M.M., Saket, P., Fuqiang, T., Alberto, V., Yongping, W., Attilio, C., Peter, L.D., Taikan, O., J., P.M., Huub, S., F., V.L.A., Ankit, A., Camila, A.-G., Ana, A., H., B.M., Manuela, B., Louise, C., Yonca, C., Serena, C., Pedro, C., Xi, C., Gemma, C., Zhao, D., Kamran, D., Moctar, D., Benjamin, D., Tatiana, F., K., G.A., Alexander, G., Mohammad, G., Thomas, G., Xiaoxiang, G., M., H.D., Joerg, H., Britta, H., Jean, H., Elizabeth, K., Megan, K., Frederik, K., Sara, L., Carmen, L.M., Alessia, M., Maurizio, M., Alfonso, M., Pablo, M., Bruno, M., Jenia, M., Farzin, N.S., Bertil, N., Merime, N.R., Christina, O., Katerina, P., Gopal, P., Olga, P., Rafael, P., Sandra, P., Elena, R., Maria, R., Nivedita, S., Adarsh, S.N., Carolina, S.B.A., Elisa, S., Lukas, S., Kai, S., Anna, S., Mojtaba, S., E., S.-S.A., Magdalena, S., Claudia, T., Thomas, T., Andrijana, T., Faranak, T., Roshanak, T., Elena, T., Ronald, v.N., Maria, V.F., Nicolás, V., W., W.D., Marthe, W., J., Y.D., Heidar, Z., Changrang, Z. and and Blöschl, G. 2025. Panta Rhei: a decade of progress in research on change in hydrology and society. Hydrological Sciences Journal, 1-27. doi: https://doi.org/10.1080/02626667.2025.2469762.
• Vorogushyn, S., Han, L., Apel, H., Nguyen, V.D., Guse, B., Guan, X., Rakovec, O., Najafi, H., Samaniego, L. and Merz, B. 2025. It could have been much worse: spatial counterfactuals of the July 2021 flood in the Ahr Valley, Germany. Nat. Hazards Earth Syst. Sci., 25(6), 2007-2029. doi: https://doi.org/10.5194/nhess-25-2007-2025.
• Macdonald, E., Merz, B., Guse, B., Nguyen, V.D., Guan, X. and Vorogushyn, S. 2024. What controls the tail behaviour of flood series: rainfall or runoff generation? Hydrol. Earth Syst. Sci., 28(4), 833-850. doi: https://doi.org/10.5194/hess-28-833-2024.
• Merz, B., Nguyen, V.D., Guse, B., Han, L., Guan, X., Rakovec, O., Samaniego, L., Ahrens, B. and Vorogushyn, S. 2024. Spatial counterfactuals to explore disastrous flooding. Environmental Research Letters, 19(4), 044022. doi: https://doi.org/10.1088/1748-9326/ad22b9.
• Guan, X., Vorogushyn, S., Apel, H. and Merz, B. 2023. Assessing compound pluvial-fluvial flooding: Research status and ways forward. Water Security, 19, 100136. doi: https://doi.org/10.1016/j.wasec.2023.100136.
• Guan, X., Nissen, K., Nguyen, V.D., Merz, B., Winter, B. and Vorogushyn, S. 2023. Multisite temporal rainfall disaggregation using methods of fragments conditioned on circulation patterns. Journal of Hydrology, 621, 129640. doi: https://doi.org/10.1016/j.jhydrol.2023.129640.

Conference papers 

• Guan, X., Merz, B., Nguyen, D., Voit, P., Heistermann, M., Vorogushyn, S. (2023): Precipitation event extremity evaluation by a cross-scale weather extremity index across Germany, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023). https://doi.org/10.57757/IUGG23-2713.
• Han, L., Guse, B., Nguyen, D., Rakovec, O., Guan, X., Vorogushyn, S., Samaniego, L., Merz, B. (2023): Hourly hydrological simulation of extreme events for 2021-flood affected catchments in Western Germany, XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023). https://doi.org/10.57757/IUGG23-2564.

Data Publication

• Nguyen, Viet Dung; Merz, Bruno; Guse, Björn; Han, Li; Guan, Xiaoxiang; Rakovec, Oldrich; Samaniego, Luis; Ahren, Bodo; Vorogushyn, Sergiy (2024): Event peak flow dataset for spatial counterfactual events, Germany. GFZ Data Services. https://doi.org/10.5880/GFZ.4.4.2024.002

Reports

• Friederichs, P., Grieger, J., Kunz, T., Ulbrich, U., Bürger, G., Buschow, S., Christ, S., Lucio Eceiza, E. E., Fauer, F. S., Feldmann, H., Guan, X., Heistermann, M., Kaspar, F., Kunz, M., Meredith, E. P., Merz, B., Mohr, S., Niermann, D., Pinto, J. G., Schröter, J., Szemkus, S., Voit, P., Vorogushyn, S. (2024): Ergiebige Dauerniederschläge und Hochwasser in Süddeutschland im Mai und Juni 2024, Berlin : Freie Universität Berlin, FB Geowissenschaften, Institut für Meteorologie, 28 p. https://doi.org/10.17169/refubium-44009
• Grieger, J., Kunz, T., Buschow, S., Daniell, J., Lucio Eceiza, E. E., Fauer, F. S., Feldmann, H., Friederichs, P., Guan, X., Kaspar, F., Knauf, J., Kreienkamp, F., Kunz, M., Lorenz, P., Merz, B., Merz, R., Mohr, S., Niermann, D., Pinto, J. G., Rakovec, O., Samaniego, L., Sauerbrei, R., Schäfer, A., Schröter, J., Szemkus, S., Tivig, M., Ulbrich, U., Vorogushyn, S. (2024): Dauerniederschläge und Weihnachtshochwasser im Winter 2023/24, Berlin : Freie Universität, 17 p. https://doi.org/10.17169/refubium-43523.