RHMS Builder is a browser-based, GIS-style graphical interface for constructing rainfall–runoff basin models using the RHMS R package (Rainfall–Runoff Hydrological Modelling System). It lets hydrologists and hydraulic engineers visually design watershed networks — placing objects on a geographic map, setting their parameters through structured forms, and generating production-ready R scripts without writing a single line of code by hand.

• GIS map canvas — place and drag nodes on dark CartoDB or standard OSM tiles.
• Typed connections — downstream flow routing and divertTo diversion targets, each colour-coded on the map.
• Rich property forms — conditional transform/loss/baseflow method panels that animate open as you switch methods, time series editors for precipitation and inflow, and 2-column matrix editors for reservoir rating curves.
• Live R code generation — topologically sorted, fully commented R script using createBasin, addObjectToBasin, and sim.
• Floating object labels — toggle node names on the map with a single checkbox.
• Contextual help — inline ? tooltips on every field explain the corresponding RHMS constructor argument.

1. Set your simulation period (start, end, by in seconds) in the top bar.
2. Select an object type from the left toolbar and click the map to place it.
3. Click a node to open its Properties panel and fill in the required fields.
4. Use Connect to draw typed links (downstream / divertTo) between nodes.
5. Click R Code to generate your complete simulation script, then copy it to RStudio.