Frankwell car park will be completely shut off to traffic over the weekend, bringing a headache to organisers of tomorrow’s Shrewsbury 10k.
People are being urged to arrive early to find alternative parking.
The race starts at 9am.
Flood warnings have been issued across Shropshire by the Environment Agency.
The red alerts include the River Severn in Shrewsbury at the Showground and The Quarry, with people being warned not to use riverside footpaths through the town.
Flood warnings are also in force further up the river on the Severn and Vyrnwy in the Maesbury, Melverley and Pentre areas.
Chris Bainger, from the Environment Agency, said: “Frankwell car park, Shrewsbury, will be closed as further flood defences are being installed. There are still 14 vehicles we advise that you move immediately.”
He said that there were 200 cubic metres (tonnes) of water a second passing through Shrewsbury this morning.
Those living downstream in the Buildwas area and as far as Upper Arley are being warned that the high water levels will be at their peak in their areas on Monday and Tuesday.
With Frankwell car park closed, a spokesman for Shropshire Council said: “Permit holders and paid tickets of this car park, can be used in the multi storey car park. Please have your ticket or virtual ticket available for inspection on exit. You will need to take a ticket on entry.”
St Julian’s near the English Bridge will only have its short stay area open with drivers asked to used Abbey Foregate car park.
Shrewsbury Park Run was also cancelled because of high river levels.
Meanwhile, park runs in Oswestry and Erddig were cancelled because of muddy ground.
River levels have risen on the Severn at the Buildwas river gauge and flooding is affecting low lying land and roads adjacent to the river from Shrewsbury to Upper Arley.
Other locations that may be affected include Coalbrookdale, Ironbridge and Bridgnorth.
The Severn’s floodplain at Leighton is starting to fill.
Elsewhere in Shropshire there are flood alerts on the River Teme, Onny and Corve in South Shropshire.
The Environment Agency is warning that flooding of roads and farmland is possible.
“Locations that may be affected include Bishops Castle, Church Stretton, Knighton and Ludlow,” it says.
Across the Welsh border there is a red, flood warning in force along the River Dee from Llangollen south, taking in the Bangor on Dee area and onto Cheshire and a lesser flood alert upstream of Llangollen.