A new spillway channel following the route of the existing channel will be built to protect the dam from larger predicted flood events in the future and a new outlet pipe will be installed, Hastings Borough Council said.
These works are expected to be finished by next spring.
The council said once the main works are complete there will be significant landscaping work which will include the replacement of the trees removed earlier this year and some new planting and reinstatement of the grassed areas used for access during construction activities.
Jackson Civil Engineering has been contracted out to carry out the works.
Andy Nailor, the firm’s contracts manager, said: “Jackson Civil Engineering are pleased to have been awarded the contract to carry out the safety improvement works to Buckshole Reservoir and are looking forward to working with Hastings Borough Council and other local stakeholders to deliver this important scheme for the town.”
The three reservoirs within Alexandra Park were built in Victorian times to supply water to Hastings.
Buckshole Reservoir, the largest of the three and the last to be built, is now more than 150 years old.
The reservoirs no longer supply drinking water, but they provide a focus for fishing, recreation and wildlife, the council said.
Cllr Maya Evans, lead councillor for environment, said: “The Environment Agency, who monitor and inspect dams, told the council that we need to undertake a number of safety improvements to Buckshole Reservoir by 2022, to help reduce the risk of flooding downstream.
“These essential works are significant, and we are working closely with the appointed contractors to ensure everything goes smoothly and that disruption is minimised.
“When the work is completed we will ensure that the trees and vegetation are replaced and allowed to thrive so that everyone can enjoy the beauty of this area of the park once again in the warmer months next year.”