"The geography, which was a feat for the Anzacs almost a century ago, remains a challenge today.
"The commemorative site is surrounded by thick scrub, steep terrain and bounded by the Aegean Sea.
"There are also heritage and conservation measures in place to preserve and protect the battlefields meaning the area cannot be expanded."
Attendances at Anzac Day services at Gallipoli have been steadily increasing and have caused pressures on facilities, with even greater interest emerging for the centenary of the first major battle fought by both New Zealand and Australian troops.
About 8500 New Zealanders and 50,000 Australians served in the campaign. More than 2700 New Zealanders and 8000 Australians died.
Snowdon said there had been calls for direct descendants to be given places at the centenary Dawn Service.
"But we believe there are probably around one million direct descendants which makes it highly improbable that many of them will be able to attend the site," he said.
"Obviously, there will be disappointments through this process because clearly I don't think we're going to be able to provide for everyone who wants to attend.
"This is not an exercise in trying to cocoon spaces for people who believe they're important."