Are Forced Evacuations a Violation of the Natural Right to Property?

After the devastation fire, flood, crime, and hurricane Katrina wracked on the city of New Orleans the mayor of that critically damaged city has ordered forced evacuations out of concern for the health of the inhabitants. The question is, is such an order constitutional. The prime amendment that addresses this issue is as follows.

Amendment IV
The right of the people to be secure in their persons, houses,
papers, and effects, against unreasonable searches and seizures, shall not be
violated, and no warrants shall issue, but upon probable cause, supported by
oath or affirmation, and particularly describing the place to be searched, and
the persons or things to be seized.

When addressing the United States Constitution you must always consider the preamble because it states the purpose for the establishment of that fine legal document. I cite it below for convenience.

We the people of the United States, in order to form a more perfect union,
establish justice, insure domestic tranquility, provide for the common defense,
promote the general welfare, and secure the blessings of liberty to ourselves
and our posterity, do ordain and establish this Constitution for the United
States of America.

According to the 4th Amendment probable cause must be established. The only part of the preamble that applies to establish probable cause in this case is general welfare. So far the mayor is right in his orders but I question the actual health risk to those whom stay. I understand that hypothetically they are a risk and a small number of those who have voluntarily evacuated have died from disease but that is hardly an epidemic. When the government built the Panama Canal 5609 deaths from diseases were recorded, yet that did not stop them from completing that great engineering feat.

The government should be issuing mandatory vaccinations and preparing for forced evacuations in the case of an actual epidemic, but a hypothetical situation is not sufficient to seize people and remove Americans from their home and thus destroy their feeling of security. New Orleans residents need to be given a chance to help rebuild their city and that can be done now as there is garbage collection and street cleaning to do if nothing else.