What is aid money for natural disasters spent on? It's often said that the best thing you can do to help after a natural disaster is to give money.  

I have a simple question about how and where that money is sent. I imagine often resources can be donated, but money is still required to utilise them. 

Is there a study showing the breakdown?
One thing such funds get spent on is corruption:

Do Public Fund Windfalls Increase Corruption? Evidence from a Natural Disaster
(Nikolova and  Marinov (2015)) 


  We show that unexpected financial windfalls increase corruption in
  local government. Our analysis uses a unique data set on flood-related
  transfers, and the associated spending infringements, which the
  Bulgarian central government distributed to municipalities following
  torrential rains in 2004 and 2005. We build an index of corruption
  using information from the publicly available audit reports, and
  exploit the quasirandom nature of the rainfall shock (conditional on
  controls for ground flood risk) to isolate exogenous variation in the
  amount of funds received by each municipality. Our results imply that
  a 10% increase in the per capita amount of disbursed funds leads to a
  12.2% increase in corruption. We also present suggestive evidence that more corrupt mayors anticipated punishment by voters and dropped out
  of the next election race. Our results highlight the governance
  pitfalls of non-tax transfers, such as disaster relief or assistance
  from international organizations, in weak democracies.


Weathering Corruption (Leeson and Sobel (2006)) 


  Could bad weather be responsible for U.S. corruption? Natural
  disasters create resource windfalls in the states they strike by
  triggering federally-provided natural disaster relief. Like windfalls
  created by the ìnatural resource curseî and foreign aid, disaster
  relief windfalls may also increase corruption. We investigate this
  hypothesis by exploring the e§ect of FEMA-provided disaster relief on
  public corruption. The results support our hypothesis. Each additional
  $1 per capita in average annual FEMA relief increases corruption
  nearly 2.5 percent in the average state. Eliminating FEMA disaster
  relief would reduce corruption more than 20 percent in the average
  state. Our Öndings suggest that notoriously corrupt regions of the
  United States, such as the Gulf Coast, are notoriously corrupt because
  natural disasters frequently strike them. They attract more disaster
  relief making them more corrupt.