The traditional 2,000-meter head race, in which several boats race each other flat-out simultaneously, was switched to a 1,500-meter time trials.
The shorter, single-file format means rowers will be using less of the river, which has been in an agitated state due to the heavy rains.
"Looking out at the water I saw logs and wood and all kinds of chunk coming down," said regatta official Harry Stinger.
"There was a tree as big as racing shell, 40 feet," said Morro, the regatta's secretary.
If the river calms down and the debris clears out tomorrow, the organizers could change course and go back to a regular format, said Dad Vail president James Hanna.
Regatta officials will be monitoring stream levels and flows in the Schuylkill headwaters in upstate Pennsylvania and eyeballing the water in Philadelphia.
Unfortunately, Morro said, not much can be done about river debris when it gets into the swim of things, other than getting out of the way.
Today racers are using only the center lane: Lane 3. The debris tends to drift toward the sides of the river.
"If they lose a boat, that's a lot of bucks," said Singer, "but the safety of the rowers is most important."
One wild card is the potential for thunderstorms later today and this evening, with more thunderstorms possible tomorrow.
The temperature is going to make a run at 80 today under genuine sunshine, and all that solar heating could fire up strong storms, the National Weather Service says.
If some rain works its way into the official gauge at Philadelphia International Airport today and tomorrow, the region would match an elite record.
The all-time spring record for consecutive days of measurable rain is 11. That feat has been matched only four times, and only once after 1900. The all-season record is 12, set in September 1889.
That standard will not be met this year, as Mother Nature has decreed that Mothers' Day will be dry.
Pete Altinger is among those who can't wait for the sun. He owns three car washes, on the Main Line, West Chester and East Norriton, and the businesses were doing fabulously well during the dry spell that ended around the spring equinox.
Since then, the rain has caused a dry spell in his cash registers.
"That first quarter was really nice," he said. "You just hate to give it back so quickly." The usually busy weekends have been particularly painful.
"I don't keep track of the weekend weather anymore, because I'm not a masochist."
Contact Anthony R. Wood at 610-313-8210 or firstname.lastname@example.org