According to Wikipedia:
The chief majority (about 90%) of Guyana's 0.74 million population lives along a narrow coastal strip in which ranges from a width of 16 to 64 kilometres (10 to 40 mi) inland and which makes up approximately only 10% of the nation's total land area.and
Drainage throughout most of Guyana is poor and river flow sluggish because the average gradient of the main rivers is only one meter every five kilometers. ... Georgetown is below sea level and must depend on dikes for protection from the Demerara River and the Atlantic Ocean.Climate Hot Map:
Guyana's capital city of Georgetown relies on seawalls for protection. When flooding occurs after large waves top the seawalls or heavy rains, sluice gates open for drainage. However, these gravity-fed gates can do so only when the tide is low enough.The sea wall
The coastal plain is home to almost all the country's agricultural production — critical for both food and export. The main crops are sugar and rice.
Sea level along the Guyana coastline is rising faster than the global average which will exacerbate future increases from further global warming.
According to Wikipedia:
The Sea Wall is a 280-mile seawall that runs along much of Guyana's coastline, and all of the coastline in the capital city of Georgetown. It protects settlements in the coastal areas of Guyana, most of which are below sea level at high tide.
Currently over topping and minor breaches at high tide are not uncommon and cause local flooding. Breaches are repaired usually in a few days. Much of the costs of building and maintaining the sea walls have been met by overseas aid. The system of dykes, drainage canals and sluice gates was begun by the Dutch in colonial times to protect sugar plantations and not as effective as it used to be. Away from Georgetown the seawall is often earth and stone.
The 2005 flood
In 2005 there was a severe flood due to intense rain which caused from two to five feet of flooding in Georgetown and large parts of the coast for weeks. According to a PAHO report "Almost 200.000 people in Guyana were affected by the floods that hit Guyana" - which is more than a quarter of the population.
And from Climate Hot Map again:
Without improved sea and river defenses and drainage systems, the coastal plains of coastal Guyana face serious flooding—if not complete inundation—owing to higher sea levels possible under worst case scenarios. Such flooding would devastate most of the population and have consequences for a large percentage of the gross domestic product.It is difficult to imagine increasing the height of the sea wall more than a few centimeters. It would probably require complete rebuilding and the cost would be very, very high.