**4. Conclusions**

In this study is observed the application of rainfall-runoff and the inundation model in Batang Sinamar River Basin. The lack of the river's geometry survey data, which are the main input for the model, can be replaced by digital measurement using satellite images. Surprisingly, this provides a good agreemen<sup>t</sup> result when it is compared with discharge observation data in two flood events. In the first scenario the model is able to catch the peak of the flow, even though in the second scenario the model is underestimated. It is proven that the NSE values for both scenarios are 0.768 and 0.531, respectively, and the correlation about 0.908 and 0.828, respectively. The result of flooding with 10-year return period has 59.963 km<sup>2</sup> inundated area and 406.72 m3/s as the highest discharge. Furthermore, in 25-year return period, the inundated area increases by about 13% or becomes 68.592 km2, and the peak flow grows to 470.74 m3/s.

This application can be a good alternative when money and time are a limited resource in the process. However, in higher decision making, surveys and field observation must be performed for the exact result.

**Author Contributions:** Conceptualization, M.F., Y.S. and A.A.K., methodology, M.F., Y.S. and A.A.K., software, A.P.A., validation, A.P.A., formal analysis, A.P.A., investigation, A.P.A., resources, M.F., data curation, A.P.A., writing-original draft preparation, A.P.A. and A.N.W., writing-review and editing, M.F., Y.S. and A.A.K., visualization, A.P.A. and A.N.W., supervision, M.F., Y.S. and A.A.K., project administration, M.F., funding acquisition, M.F. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Institute for Research and Community Services of Institut Teknologi Bandung (LPPM ITB) through ITB Excellent Research 2023 and by the Indonesia Endowment Funds for Education (LPDP) through gran<sup>t</sup> scheme PRJ-102/LPDP/2021.

**Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Digital elevation model, soil type and land use classification data downloaded freely from Indonesia Geospatial Information Agency site in Indonesia Geospatial Portal. Rainfall and discharge observation data received from West Sumatera Water Resources Agency.

**Conflicts of Interest:** The authors declare no conflict of interest.
