Like one of those ancient European cities, this bustling metropolis about 125 miles south of St. Louis has erected a high wall between itself and extinction. Completed in 1964 by the Army Corps of Engineers, the wall was built to stem the cocoa rage of the Mississippi River, which threatens the lives and livelihoods of the Cape's 36,000 citizens.

But to hear the town leaders talk, they would just as soon take their chances against the river and the occasional flash flooding of local creeks than to become involved with the federal government's well-intentioned flood insurance program.

Indeed, Cape officials are so angered by what they view as federal intrusion that the town has joined developers, realtors and other townships from 14 states in raising about $200,000 toward financing a suit against the flood insurance program.

Called the Flood Insurance Litigation Coalition, the conservative, anti-government group has an important - and an unlikely - ally in liberal-leaning Sen. Thomas F. Eagleton (D-Mo.)

Last week, Eagleton was the leadoff witness before the Senate Banking Committee at hearings on whether to renew financing of several programs run by the Department of Housing and Urban Development, including flood insurance, which expires June 30.

Eagleton is known for his dogged persistence in certain causes. Even so, his opposition to the flood insurance program is so vehement that he has confounded not only his fellow legislators in Washington, but others as well.

"If you find out why he is so interested in our cause, let us know, will you?" says an obviously delighted Thomas M. Utterback, the Cape's 30-year-old city attorney.

It is not a big vote-producing issue, because it is basically a small-town concern. Besides, Eagleton does not face election again until 1980, and most of the votes in his 1974 victory came from the St. Louis and Kansas City areas.

Yet two weeks ago, at hearings in Washington and the Missouri capital of Jefferson City, Eagleton attacked the program in bitter, often caustic language as if his political career depended on it.

Eagleton's sharpest barbs were saved for the acting federal insurance administrator, J. Robert Hunter.

The Federal Insurance Administration (FIA) occupies a tiny corner of the massive bureaucracy at the Department of Housing and Urban Affairs. By federal statute, insurance regulation has been relegated to state authorities, but the FIA was created in 1968 ot oversee federally subsidized insurance coverage that private companies refused to handle without government help - riot, crime and flood insurance.

Hunter, whose outspoken criticism of high insurance rates has upset that industry, generally is respected on Capital Hill as an able, hardworking administrator. But he is a staunch supporter of the flood insurance program, and for this he has incurred Eagleton's wrath.

Eagleton wants President Carter to replace Hunter, and tweleve days ago at Jefferson City he told the hearing, "I'm hopeful some changes will be made (in the administrator's office) in the very near future."

What apparently troubles Eagleton and his followers about the federal flood insurance program are the sanctions that were attached to the law to force communities to enter the program. But Congress wrote sanctions into the Flood Disaster Protection Act of 1973 because experience proved nobody would buy the insurance without being forced into it. People who lived in flood-prone areas simply played roulette or relied on the government to provide costly disaster assistance.

Though government-subsidized flood insurance policies became available in 1968, there were few buyers. By mid-1972, fewer than 3,000 of the 21,000 flood-prone communities had joined the program, and fewer than 275,000 homeowners were insured.

As a study called "Limited Knowledge and Insurance Protection" by the Wharton School at the University of Pennsylvania notes: "Although Rapid City, N.D., qualified for the program in 1971, only 29 policies were in the force at the time of the disastrous flood in June 1972. Only 683 policies were sold in Pennsylvania prior to Tropical Storm Agnes."

The chain of disastrous floods in 1972 - Rapid City, Agnes, and Buffalo Creek, W. Va. - caused Congress to pass the 1973 act after about one year of hearings.

Among the provisions of the law:

No federal financial assistance for construction or acquisition of buildings in areas designated as flood-prone to communities that do not join the program.

Homeowners in flood plains must buy insurance as a condition for obtaining new FHA, VA or conventional loans from federally-insured or supervised lending institutions.

As a result, there has been a dramatic change in the number of participants in the program. There are 1 million policyholders and $30 million of insurance in force.

Under the terms of the program, communities with flood problems must vote to participate. But in certain communities of Missouri and a few other states, local government have virtually no say over such matters as zoning and planning.

Indeed, in many Ozark communities, there is no such thing as zoning. And there is broad opposition to the flood insurance program - especially from citizens living on high ground - because it smacks of planning. They fear that planners are after their most valued possession, the land.

Often, the most vocal opponents of the program are small-town officials with commercial interests that might be hurt by the program's limitation on land development in flood-prone areas. For example, when Eagleton recently held hearings at Caffville, Mo., the most vocal critic of flood insurance, that town's city attorney, also happened to be on the board of directors of the local commercial bank. Commercial bank lending to areas subject to flooding is limited under the current law, but that limitation would be eliminated under Eagleton's proposed amendment.

For the past two years, the Missouri legislature has voted down bills that would have altered the law to allow people with flooding problems in these communities to join the program. A bill presently before the state senate is expected to be voted down again.

But these counties are notable exceptions. Nationally, some 15,500 flood-prone communities are in the program, while only 500 have not joined. Indeed, the FIA estimates that better than 95 per cent of the areas vulnerable to flooding are in the program and, so far, $188 million in claims have been paid.

Although no statistics are available, the FIA believes that the highly subsidized insurance coverage will prove far cheaper to the government than paying disaster relief. Moreover, the agency believes the insurance avoids the vagaries of presidential disaster relief proclamations under which one county often gets help while a neighboring county does not.

At last week's Senate Banking Committee hearings, Eagleton proposed about a dozen changes in the present law. One Eagleton proposal would allow banks to offer mortgage loans or improvement loans to business or homes located on flood plains that have not taken out flood insurance. Under the present law, such loans would not be permitted because they are federally insured. Eagleton argues that there is no evidence that any bank has had to turn to the Federal Deposit Insurance Corp. because of flood-caused defaults.

Eagleton had proposed a similar amendment, among others, to the act last year, but it was voted down. George K. Bernstein, a Washington attorney who was the first federal insurance administrator and who served until 1974, testified that the Eagleton amendment would allow banks "to make loans to unsafe and uninsured flood-prone structures, and developers would actually be encouraged once again to indulge in hazardous construction in identified flood-prone areas."

Under the insurance program, the first $35,000 worth of insurance coverage on existing structures would be subsidized; after that, insurance is figured on the normal actuarial basis. There is no subsidy for insurance on new structures put up in flood plains. This is meant to discourage construction in flood-prone areas.

A new building in a flood plain will be financed by a federally insured bank only if the foundation or landfill raises the structure above the highest level of flooding in the area during the past 100 years. These levels are figured by the Corps of Engineers, which is helping to survey all of the nation's flood plains for the insurance program.

Insurance policies are issued by the National Flood Insurers Association (NFIA), a pool of about 130 major insurance companies that carry the small, unsubsidized portion of flood insurance.

The General Accounting Office, at the request of HUD, recently did a study of NFIA's finances. It found that the NFIA's books were badly scrambled due mainly to a faulty computerized accounting system set up by a private subcontractor.

Recently, with the Capitol emptied for the Easter recess, Eagleston alone presided over the first of three hearings by his Subcommittee on Government Efficiency on the GAO report.

Eagleton's frustration with the program was evident. In various references, he said that it was "maladroitly handled," that the public might have been "ripped off," and that it has been "messed up by the FIA."

For about three years, Eagleton has attacked the program in the Congressional Record, and fired off acerbic letters, first to HUD Secretary Carla A. Hills and now to Patricia R. Harris. In a Sept. 26, 1975, letter to Hills, he accused her of "breach of promise" for not honoring an alleged commitment to him to support changes in the program.

Hills denied any deal, adding: "I also urge you to consider the severe hardships that would be imposed on the communities throughout the nation, including 297 in the State of Missouri, should the emergency flood program, which has unanimous support, be permitted to expire."

More recently, Eagleton cited the GAO report on the program's finances in a critical letter to Secretary Harris. She wrote back endorsing the program, and Eagleton has made derisive references to her reply at various hearings.

The GAO report on the program's accounting was not the first time that agency has figured in Eagleton's war with the FIA and with acting administrator Hunter.

The federal insurance administrator has been an appointed post, not subject to Senate confirmation. But once Hunter was named by President Ford, Eagleton pressed the GAO to determine whether Senate confirmation is called for. The GAO concluded that the administrator should indeed be confirmed by the Senate.

It remains to be seen whether the Carter administration will reappoint Hunter, who is waiting for word on his future from the White House. If Carter does reappoint him, it will be over the strong opposition of Eagleton. The question is whether Hunter will be able to find allies who have fervor to match Eagleton's.

Meanwhile, here in Cape Girardeau, few of the citizens with homes and businesses located in flood-prone areas have bothered to take advantages of the available flood insurance.

On March 27, after a heavy rain, Cape LeCroix Creek, which runs through town, overflowed and caused record flooding in 62 businesses and 115 homes, most of which were uninsured.

As a result, even as Cape Girardeau officials press their suit against the flood insurance program, they are requesting more than $2 million in federal disaster assistance for homeowners and businessmen who did not bother to take out insurance.