It's an instinctive, and laudable, impulse. But be careful, say experts, because a disturbing amount of charitable giving creates more headaches than it helps.
"If you go to a lot of disasters, as I do on a regular basis, you are going to find out talking to first responders that their number one issue is inappropriate disaster aid," said Jose Holguin Veras, an engineering professor and director of the Center for Infrastructure, Transportation, and the Environment at Rensselaer Polytechnic Institute. "They continually refer to that as the second disaster."
Holguin Veras can rattle off a list of inappropriate donations he has seen at disaster sites: "wedding gowns, tuxedos, broken bikes, broken medical equipment, expired medications, undrinkable drinks." He said he even came across a tiger costume—and that a fellow disaster-response expert recalls seeing a truckload of sex toys.
By Holguin Veras' estimate, "around 60 percent of the total amount of goods that arrive after disasters is completely useless and should not be there."
Even apart from the type of item you donate, the sheer volume of so-called in–kind donations can be a problem at disaster sites. If an area needs water to be trucked in, piles of donated clothing clogging roadways or depots can make that harder.
After Superstorm Sandy struck last fall, the Red Cross explicitly asked people not to make material donations. "These items often must be sorted, repackaged, and transported, which impedes valuable resources of money, time, and personnel that are needed for other aspects of our disaster relief operation," its web page said.
In the aftermath of the shooting at Sandy Hook school in Newtown, Connecticut, donors sent so many teddy bears, stuffed animals, and school supplies that the town finally asked for the gifts to stop. Town officials managing the donations had been sending items the town couldn't use to others in need—even, by some reports, to homeless children in India. They only finished the task in late March.
Disaster relief experts say that monetary donations are by far the most effective way to help after a disaster. Charitable organizations on the ground know what supplies are needed, and more funding helps them be more effective. But even giving money can be tricky.
Fraudulent charities claiming to help victims crop up regularly after disasters, and the rise of social media has only made it easier for them to prey on charitably minded people.
The Better Business Bureau issued a warning just a day after the Boston marathon bombings, saying that "at least one poorly-conceived charity scam has already emerged in the wake of the explosions at the finish line of the Boston Marathon yesterday, and more are likely."
Actually, more were in the works already. Just four hours after the Boston marathon bombing, "over 125 domain names were registered to collect money for the victims and several fraudulent twitter accounts were opened asking for money as well," according to reports received by Massachusetts' undersecretary of consumer affairs.
So how can you make your good intentions count? Stick to reputable organizations that are active in the area where the disaster strikes. Charity evaluators like charitynavigator.org and the Better Business Bureau's Wise Giving Alliance can offer suggestions. Sometimes officials will create a charity to help with disaster response, as Massachusetts officials did last month when they launched The One Fund.
Also, remember that disasters often have prolonged impact, so you can consider waiting to give until it's clear which organizations are proving most effective.
"Giving all happens within eight to ten weeks after a disaster, and then pretty much dissipates after that," said Bob Ottenhoff, chief executive of the Center for Disaster Philanthropy. "Your donation might be just as valuable a week from now or a month from now as it might be in the passion of the moment."
The bottom line: Disaster aid is great—as long as it is really helps.
—By CNBC's Kelley Holland