The Dutch Resistance to Flood, part 1: Zuiderzee Works

    Half of Holland lies below sea level or a meter above sea level, yet it remains the most resilient nation to flood, both by ingress of seawater and swelling of rivers, and the Dutch remain the most prolific farmers with agricultural exports of the nation totaling 95.6 billion Euros in 2020. The Dutch have reigned sea, and tamed rivers; they have triumphed over petty squabbles of Poseidon and Athena. Indeed, the gods created the world, but the Dutch built Holland. 

    First, let's look into how they reigned the sea. Two major civil engineering works: Zuiderzee works and the Delta works, collectively dubbed as one of the seven wonders of modern world, have made Netherlands immune from vagaries of sea. Zuiderzee works dam the large shallow entry of North Sea into Netherlands which prevents flood by high tides, and has facilitated reclamation of land (165,000 ha until 2021). Delta works are much more of defensive nature, shortening the Dutch coastline by construction of hydraulic structures like dams, sluice gates, and storm surge barriers, thus reducing the length of dikes to be raised.

    Zuiderzee works

    As a response to huge losses by recurrent flooding due to ingress of the Northern sea through the shallow entries of the Zuiderzee, the Dutch government went ahead with the plan to enclose the Zuiderzee. Construction works began from 1927. Afsluitdijk a 32km long, 9m wide dam rising upto 7.25m above sea level  was built across the Zuiderzee, successfully enclosing it from the North Sea and converting Zuiderzee- also known as the Southern Sea- into a freshwater lake, IJsselmer. 

Zuiderzee works. The black lines on North West represent the Afsluitdijk dam

Zuiderzee works

                           
    Construction of the dam was started from four locations- two from both sides of mainland and two from man made islands constructed for the project. Till- unsorted glacial sediment- was used as primary material for structure due to its better structural performance compared to sand or clay, and its availability at bottom of Zuiderzee. Till was deposited into seabed by boats in two parallel lines, and sand was deposited between the lines. After the structure rose above water level, it was covered by another layer of till. The dam was raised to required elevation by using clay and sand. Basalt rocks were used to form a protective layer at base, and grass was planted on sloping surface to prevent erosion. Construction of the dam was completed on 1933, two years before the targeted date.

Construction of the Afsluitdijk dam

Road connecting Friesland and North Holland was built over the dam; ship locks were built to keep marine trade unhindered; and twenty five discharge sluices were housed to discharge the IJsselmeer lake, which is constantly being fed by the IJsselmeer river- its namesake- and other streams into the North sea.

Drainage Sluices

    

Pictorial Representation of Afsluitdijk

Road connecting Friesland and North Holland 

    Alfsluitdijk- the dam- is only half of the wonder; the other half of the undertaking is land reclamation which has made the Netherlands the second largest exporter of agricultural products. The Dutch have been reclaiming land from the sea and lakes since ages: from 1200-1900 AD, 380,000ha land had been reclaimed; 17% of total land of the Netherlands is reclaimed. Some ambitious Dutch had been dreaming of reclaiming the Southern Sea since the 17th century. The flood of 1916, food shortage during World War I due to supply chain disruption, and public support of Queen Wilhelma, the first female billionaire, acted as the impetus to spur the lofty dreams of few into a national plan. Soon enough, ingenious engineering materialized the plan. It must be mentioned with utmost reverence that, Cornelis Lely, an engineer and a cunning politician, played a significant role in implementation of the Zuiderzee works. 

Land reclamation works in the Zuiderzee

    Four polders (a Dutch word meaning low lying land reclaimed from sea or lake)-Wieringermeer (200km2), Noordoostpolder (480km2), Eastern Flevoland (540km2), and Southern Flevoland (430km2)- totaling 1650km2 have been constructed since 1926. The first to be constructed was the Wieringermeer polder. First, an encircling dike was constructed around the required area. Then it was drained by pumping stations. A network of  drainage canals, in the form of small ditches leading to larger canals were built to drain the remaining shallow water. The loss of moisture caused some part of land to sink by up to a meter. After the settlement of soil, underground drainage channels were laid below the drainage channels befitting the demands of agricultural land. Then, the land was developed into agricultural land. The land was divided into several plots, each plot being accessible by road in the front and canal in the back. The best plots of land are used for vegetable production, next best for rye and other grains, and the worst land forested. Other polders were constructed using the similar techniques. However, planning of settlement differed as the study of sociology progressed along with settlement of polders in Netherlands, and the importance of sociology in planning of efficient settlements was not realized in early days of the Zuiderzee works. A new urban settlement called Almere, occupying 25% of the total land of the polder, was developed in the Southern Flevoland to address housing shortage and overcrowding of the old land, especially Amsterdam.  

Urban area developed in reclaimed land

Reclaimed land used for farming

    Originally five polders were planned to meet agricultural needs of the country. However, development of efficient modern agricultural techniques rendered the fifth polder obsolete. Further, environmental concerns resisted construction of the fifth polder. It seems the Dutch, with ingenious engineering, have answered to Tolstoy. 

    The enclosure and land reclamation works completed the Zuiderzee works, and have ensured safety of Northern Holland from flood for the last 85 years. The South, however, remained unprotected. A national tragedy struck the Netherlands on 1953 which incentivized an even greater, even magnificent work of engineering, the Delta works. More on that later. See you in the next blog!