The Office for the Coordination of Humanitarian Affairs (OCHA) is tasked with coordinating the humanitarian aid delivered by United Nations agencies and ensuring the coherence of all humanitarian action in crises. The role of the OCHA was reinforced by the humanitarian reform of the United Nations in 2005 . It is rests upon three main ideas :

 Achieving a mechanism of rapid financing for humanitarian emergencies as a result of the implementation of the CERF: the Central Emergency Response Fund for serious crisis (urgent or sudden disasters) or underfinanced crisis (within a limit of a third of the CERF funds). The fund reinforced the ability to give rapid financing answers,. It stands in compliance with the logic of humanitarian assistance coordination. The CERF is only accessible to UN agencies. It is not intended to substitute for their budgets.
 Organising a humanitarian coordination, based on the Office for the Coordination of Humanitarian Affairs (OCHA). OCHA does not lead operational activities of its own. In New York, OCHA reports to the Security Council on the humanitarian situation in a given region or country. In the field, its representatives hold regular consultation meetings with various humanitarian players, attended by NGOs and the International Committee of the Red Cross (ICRC). OCHA also appoints humanitarian coordinators to better assess needs and choices on assistance strategy. It represents the Emergency Relief Coordinator in the country of operation. However, in practice, many humanitarian coordinators hold the function of Resident Coordinator (referring to the UNDP) and/or of representative of a UN agency in the given country.
 Improving humanitarian aid in the field by implementing clusters that allow inter-agency coordination (a leader Agency is appointed for each theme according to its competence). For every aspect of humanitarian intervention (health, shelters, education and so on), the clusters must allow coordination between relevant actors in the area of operation.

Both the CERF and the Consolidated Appeal Process (CAP) provide financing: they raise annual funds to help contributors schedule, implement and control their activities. They also allow the beneficiaries to monitor distributed aid and Flash Appeals, to structure humanitarian aid coordination during the first three to six months of the emergency period. These two financing mechanisms are also managed by OCHA.

To address natural disasters, the UN humanitarian system also relies on the United Nations Disaster Assessment and Coordination (UNDAC), whose role is to identify a body of humanitarian professionals, working for the United Nations, other organisations or governments around the world. The UNDAC appeals to this body to provide assistance during humanitarian crisis in the immediate aftermath of a natural disaster. The UNDAC forwards information regarding the nature of the disaster and the assessment of the situation, enabling the OCHA to coordinate the humanitarian response.

Update : July 2010