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CONTRIBUTING.md

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+# Contributing to rfaR
+
+Thank you for your interest in contributing to rfaR! We welcome bug reports, feature requests, validation results, and other feedback from the community.
+
+## Review Capacity
+
+rfaR is maintained by a small team within the U.S. Army Corps of Engineers Risk Management Center (USACE-RMC). **Our capacity to review external pull requests is very limited.** We prioritize issues and bug reports, which are always welcome and will be reviewed as resources permit.
+
+If you plan to submit a pull request, please open an issue first to discuss your proposed change. This helps avoid duplicated effort and ensures your contribution aligns with the project's direction.
+
+## How to Contribute
+
+### Report a Bug
+
+If you find a bug, please [open an issue](../../issues/new) and include:
+
+- Steps to reproduce the problem
+- Input data and configuration (if applicable)
+- Expected behavior vs. actual behavior
+- R version, rfaR version (`packageVersion("rfaR")`), and operating system
+- Any relevant error messages or screenshots
+- A minimal reproducible example (`reprex`) when possible
+
+### Request a Feature
+
+Feature requests are welcome. Please [open an issue](../../issues/new) describing:
+
+- The use case or problem you are trying to solve
+- How you envision the feature working
+- Any references to statistical or hydrologic methods or published literature
+
+### Report Validation Results
+
+Given the life-safety applications of this software, independent validation is especially valuable. If you have compared rfaR results against other software (e.g., RMC-RFA, HEC-HMS, HEC-WAT, published tables, or analytical solutions), we would appreciate hearing about it through an issue.
+
+### Submit a Pull Request
+
+Pull requests may take several weeks or longer to review. Before submitting code:
+
+1. **Open an issue first** to discuss the proposed change
+2. **Follow the coding standards**, including roxygen2 documentation on all exported functions
+3. **Include unit tests** using `testthat` that validate against known results (RMC-RFA, HEC-HMS, published tables, or analytical solutions)
+4. **Ensure a clean `R CMD check`** with zero errors, zero warnings, and zero notes (run via `devtools::check()`)
+5. **Rebuild documentation** with `devtools::document()` before committing
+6. **Follow existing code style** (explicit `package::function()` namespacing, positional column access where appropriate, and the package's established plotting conventions)
+
+## Developer Certificate of Origin
+
+By submitting a pull request, you certify under the [Developer Certificate of Origin (DCO) Version 1.1](https://developercertificate.org/) that you have the right to submit the work under the license associated with this project and that you agree to the DCO.
+
+All contributions will be released under the same license as the project (see [LICENSE](LICENSE)).
+
+## Federal Government Contributors
+
+U.S. Federal law prevents the government from accepting gratuitous services unless certain conditions are met. By submitting a pull request, you acknowledge that your services are offered without expectation of payment and that you expressly waive any future pay claims against the U.S. Federal government related to your contribution.
+
+If you are a U.S. Federal government employee and use a `*.mil` or `*.gov` email address, your contribution is understood to have been created in whole or in part as part of your official duties and is not subject to domestic copyright protection under 17 USC 105.
+
+## Security
+
+If you discover a security vulnerability, please do **not** open a public issue. Instead, contact the RMC team directly through official USACE-RMC channels.
+
+## License
+
+See [LICENSE](LICENSE) for details. This software is provided by USACE-RMC under a BSD-3-Clause license with a no-endorsement clause.