Though not indicative of sea-level change, or speculation of such, during the later-empire many Roman ports suffered from what contemporary writers described as 'silting'. The constant need to dredge ports became a heavy burden on the treasury and some have speculated that this expense significantly contributed to the eventual collapse of the empire. Roman salt works in Essex, England, today are located at the five-metre contour, implying this was the coastline.[10][11] These observations only indicate the extent of silting and soil rebound affecting coastline change since the writing of De architectura.