An Iowa State University expert says relief workers in areas affected by hurricane Harvey are bracing for a "secondary disaster." Supply Chain Management Professor Johanna Amaya Leal says every major disaster since 1920 has seen a flood of unneeded, unwanted, and unusable donations, taking time and resources away from helping people. She says it's a good idea to talk to with faith-based or civic organizations with contacts in the disaster area to know what's needed before making a donation. When in doubt, Leal says the best thing people can give in times of disaster is money.