These are links we used to plan realistic and plausible scenarios for disaster response and emergency management exercises. These links are by no means complete, but they are easy to work with and produce realistic assumptions.
One of the most basic requirements to calculate scenarios are basemaps. They need to be georeferenced. QGis is a free Geographic Information System. It offers free maps, satellite images and Digital elevation models. Plugins allow basic calculations.
Earthquakes are very common large scale disasters. Open Quake from the Global Earthquake Model Foundation can be used to estimate consequences. It is freely available software that integrates in QGis. It comes with online documentation and many online tutorials.
The International Atomic Energy Agency (IAEA) has a very good publications database. The website has the accident and incident reports from the past decades. The Technical Documents (Tecdocs) are a treasure trove for factors and formulas to estimate consequences after a radiological or nuclear release.
The US Army Corps of Engineers provides a Hydrologic Engineering Center (HEC) homepage. This site allows to download free software that can perform hydrologic analysis. The site also offers tutorials, online classes, etc…
This is a great site to model floodwaves, floodings, dam breaches, …
The US Environmental Protection Agency publishes freely available software to model hazardous materials releases. One word of advice, ALWAYS note which version of chemical database you use, with new research threshold values can change dramatically. The suite integrates maps and can also be used to manage areas and facilities. ALOHA allows to calculate toxic, flammability areas and heat radiation.
When planning exercises, the knowledge of daylight and twilight periods are helpful. While there are many ways to find out, here is a comprehensive website easy to work with.
The Dutch research institute has produced the colored books. This is a series of books, that lay the foundation for risk and consequence analysis as we know today. Those books are downloadable at Gexcon, download requires a free registration.