NEW YORK (CNN/Money) - With President Bush promising massive aid to rebuild the devastated Gulf Coast, investors are eyeing what companies stand to benefit from the rebuilding process.

In the days after Hurricane Katrina, investors snapped up stocks that might see an upside from the rebuilding process -- especially those in key industries like construction, machinery and building products.

"The boom is going to be enormous," said Marshal Cohen, chief industry analyst at market research firm the NPD Group. "We're going to see a regentrification of the whole region, and local governments will come in and rezone and rebuild. Big national retailers and home improvement outlets will see the benefits first."

The four hurricanes that hit Florida in August and September of last year serve as a good predictor of which sectors will see a boost in business after Katrina.

"The home improvement sector really benefited in Florida last year," said Jay McIntosh, a retail analyst at Ernst & Young. "We're a very self-reliant country and people start fixing their places very soon."

A study of the four costliest hurricanes before Katrina by Ned Davis Research found that three subsectors had outperformed the market six months after Andrew, Charley, Ivan and Hugo.

The contract oil drilling sector averaged a 36.2 percent gain. Oil and gas exploration and production averaged 26.5 percent gains. And building products averaged a 14.2 percent gain over the period.

Big retailers in the home improvement market -- Home Depot, Lowe's and True Value -- will see the benefits as residents rebuild with proceeds from insurance and federal and local aid, some analysts said.

Lowe's (down $0.70 to $62.43, Research) stock is up 1.7 percent since Katrina hit on Aug. 29th, and saw several large single-day gains over that period, before declining back near pre-Katrina levels last week. Its price-to-earnings ratio is currently 21, high for the home improvement industry, whose average P/E is 16, according to Thomson/Baseline.

Home Depot (down $0.36 to $38.35, Research) is actually down 1.3 percent since Katrina, with a P/E of 16. But the company's one-year forward P/E -- price divided by predicted earnings -- is 13, slightly lower than the average. True Value is privately owned.

Among oil companies, Exxon Mobil (Research), Royal Dutch Shell (Research), BP (Research) and Chevron (Research) have all seen significant stock gains since Aug. 29. Royal Dutch Shell is up 5 percent. Chevron and BP have both gained 8 percent, and Exxon has risen 10.6 percent.

In the immediate wake of the hurricane, the federal government has contracted with a number of companies to provide rebuilding and other services, including The Shaw Group, Fluor Corp., Bechtel National, CH2M Hill and Dewberry Technologies.

The Shaw Group (down $0.32 to $22.00, Research) received a $100 million emergency FEMA contract for housing management and construction. (Full story)

The stock, up 27.5 percent since Aug. 29th, has a P/E of 150, based on a poor third quarter with large charges. If it meets its earning predictions in the coming year its P/E will be 19 -- less than the construction & engineering industry's average of 34, according Thomson/Baseline.

Fluor (down $0.68 to $59.82, Research), which also received a $100 million FEMA contract, will provide temporary housing and communication tools for the hurricane's victims. Its stock is up 4.8 percent since Katrina with a P/E of 41 -- well above the industry average 26.

Bechtel, CH2M Hill and Dewberry Technologies are privately owned.

Major companies whose equipment and products will be used in the rebuilding effort -- Caterpillar (Research) for machinery and Weyerhaeuser (Research) for lumber -- have seen a boost in the last two weeks. Caterpillar is up 7.5 percent and Weyerhaeuser is up 5.9 percent.

And because New Orleans' water supply is so contaminated, companies with purification products are looking brighter as well. Tetra Tech (down $0.19 to $16.53, Research), which specializes in water infrastructure projects, has risen 9.8 percent since Katrina.

Major public properties will need restoration as well.

"Government-owned facilities like naval facilities and shipyards are going with their existing relationships," said Poe Fratt, senior analyst with AG Edwards. "But many of the decisions about reconstruction are happening at the state level, so those outcomes are still up in the air."

The Halliburton (up $0.32 to $66.25, Research) subsidiary KBR received a $500 million contract from the Navy to rebuild facilities in Mississippi and New Orleans. Its experience in construction, oil and project management make it a potential beneficiary of rebuilding.

However, it is not well-suited to residential projects.

"The larger reconstruction effort is a bit out of Halliburton's scope," said Michael Urban, analyst with Deutsche Bank. "But their oil field services company will benefit from oil redevelopment and the restoration of refineries."

_______________________

For a look at how Bush is grappling with the reconstruction plan, click here.

For all the latest headlines on Markets, click here.

Analysts quoted in this story do not own shares of the companies they've discussed and their firms have not performed investment banking for the companies during the past 12 months.