What is SplashTool?
SplashTool is software for iterative, volume-consistent calculation of runoff paths and water depths in terrain depressions during heavy rainfall events.
What advantages does SplashTool offer compared to similar software?
SplashTool enables volume-accurate runoff path analysis with significantly higher explanatory power than classic flow path analyses (for example, those based on the ArcGIS Spatial Analyst). At the same time, the required effort is far lower than for full hydrodynamic simulations, even for very large study areas. This allows you to identify key runoff paths and relevant terrain depressions at an early project stage with minimal effort. The results reduce effort in subsequent steps such as plausibility checks, remote sensing and interpretation of runoff-relevant structures, preparation of site inspections, and delineation of sub-catchments.
Is SplashTool standalone software or a GIS plugin?
SplashTool is standalone software. It does not require costly software such as ArcGIS with the Spatial Analyst extension. To use the GPU computing core, an NVIDIA graphics card is required (see the configuration and installation guide in the Downloads section). For preparation of input data and visualization of results, a geographic information system (GIS) is required. Any GIS capable of handling GeoTIFF files can be used, such as ArcGIS or the free QGIS.
Can SplashTool be integrated into my GIS?
SplashTool uses standard GIS formats that can be easily imported and further processed in GIS environments. For enhanced convenience, two dedicated integrations are available:
- The QGIS SplashTool Result Loader enables straightforward import and symbolization of SplashTool results. The plugin can be installed directly from the official QGIS Plugin Repository.
- Through a partnership with Rehm Software, SplashTool results can be seamlessly integrated into ArcGIS Pro using FLUSS.
How do I get started?
- Request a demo license via the Downloads page
- Download the installation guide, process description, and setup file from Downloads
- Download the sample project from Examples or use your own data
- Follow the workflow using the video tutorials on YouTube (external link).
How much does SplashTool cost?
The current annual usage fee is listed here.
What are the licensing terms?
SplashTool is licensed per computer as an annual single-user license. An additional “Education” license is available for universities and colleges. A sample license agreement can be provided in advance upon request via the request form.
Can SplashTool be used to create heavy rainfall hazard maps according to the guidelines of Baden-Württemberg, NRW, or Hesse?
SplashTool is suitable for simplified hazard assessments in accordance with DWA-M 119, Chapter 7.2.4, and provides volume-consistent results. It is not a hydrodynamic simulation model and does not calculate flow velocities. Therefore, it cannot replace hydrodynamic models where such simulations are required by official guidelines. In practice, SplashTool is widely used in Baden-Württemberg, Hesse, and NRW as an upstream rough-analysis tool prior to detailed hydrodynamic simulation. Large areas can be analyzed holistically at an early project stage, supporting system understanding, identification of main runoff paths and depressions, and localization of runoff-relevant structures. This early-stage rough analysis provides substantial added value and is a core focus of SplashTool development.
Do I need an NVIDIA graphics card to use SplashTool?
The GPU computing core is based on NVIDIA’s CUDA architecture. AMD graphics cards are not supported. Depending on area size and system configuration, iteration times are typically 20 to 100 times faster on an NVIDIA GPU than on the CPU. The CPU computing core is no longer actively developed; therefore, an NVIDIA graphics card is strongly recommended.
How long does an iteration take, and how much VRAM is required?
The following table shows examples from real projects. VRAM indicates the GPU memory used during iteration. Actual runtimes depend strongly on terrain characteristics and hardware configuration. All areas were calculated as complete domains without subdivision, based on a 1 × 1 m grid (1 million cells per km²).
| Area Size | Terrain Structure | Graphics Card | Computation Time | Required VRAM |
| 38 km² | Partially moderate, partially rugged topography | NVIDIA RTX 4080 | 30 min | 1.8 GB |
| 450 km² | Largely flat topography with rugged peripheral areas | NVIDIA RTX 4080 | 3 h | 10 GB |
| 1,000 km² | Approx. 50% rugged topography with gorges, approx. 50% flat terrain | NVIDIA RTX 3090 | 26 h | 20 GB |