Donate money, medicine, blankets, food or other supplies to charity organizations helping flood victims. The most active organizations in this respect are the Red Cross, World Food Program, Church World Service, Oxfam, Save the Children and UNICEF. Donating money is seen more beneficial because charity organizations on the ground are better placed to judge what supplies or services are needed. Charities typically post how they spend the donated money on their websites, so you can determine if, in your view, a particular organization spends the funds wisely or not.
Buy goods that were made in the affected country or region. For example, you could help the Pakistani economy by buying the goods the Pakistanis produce (textiles) and crops they grow (rice).
Sign up as a volunteer for charity work in the affected areas. If you have some spare time and want to help as a volunteer, offer your services to the charity organizations listed in Step 1. You can help distribute food or work as a nurse. Apart from doing a good deed, you will burnish your resume and reputation in the eyes of colleagues, friends and family.
Help the environment. Some scientists believe an increased amount of floods in some areas in the 2000s is a result of global warming, which may be attributed in part to carbon dioxide emissions generated by human activity. For example, a 2009 research paper in the journal "Geophysical Research Letters" by P. Allamano, P. Claps, and F. Laio analyzed runoff data recorded by 27 stations in the Swiss Alps and came to the conclusion that large floods were more frequent than in the past and were associated with rising global temperatures. Accordingly, by cutting your energy consumption, you can help reduce the amount of fossil fuels burnt to produce energy, thus helping the environment and indirectly reducing the flooding itself.