Solutions against flooding of rivers

Rivers ecosystem is an essential part of our nature. Rivers are not only a source of water, fishery but actually are arteries of any country used as shipping lanes for delivery of goods. But the river's unpredictable behavior can lead to disasters, devastating adjacent inhabited areas. Branch Manager of Van Oord in Russia Anko Bos told IAA PortNews about river floods prevention measures and solutions provided by Van Oord in the Netherlands and elsewhere.

Introduction
There are many rivers in Russia, which are part of the hydrological cycle and usually contains freshwater, which is flowing towards an ocean, a lake, a sea or another river. Any disruption in this cycle could cause flooding as it occasionally does on amongst others the following rivers: Kuban, Lena and Amur Resulting in causes varying from discomfort to total devastation.

Flooding is a natural part of a river's cycle. In many developed areas, human activity has changed the physical characteristics of the river channel, altering different magnitudes and frequencies of flooding. Some examples of this are the building of levees, building on floodplanes,the straightening of channels, and the draining of natural wetlands. And  have as a result dramatically increased the risk of flooding of the river.

Straightening rivers allows water to flow downstream more rapidly increasing the risk of flooding places further downstream. Building on flood plains removes flood storage which again exacerbates downstream flooding. The building of levees may only protect the area behind the levees and not those further downstream. Levees and flood-banks can also increase flooding upstream because of the back-water pressure as the upstream flow is impeded by the narrow channel banks.

Any surplus of precipitation will add to the risk of flooding. The winters form an additional risk as the precipitation is being stored until the moment the winter stops and the surplus of meltwater is offered.

Dutch Delta
In analogy to this The Netherlands, being a river delta and for about 50% below sea level, and acting as Europe’s drainpipe with its rivers Rhine, Scheldt and Meuse, needs to safely accommodate the discharge flows coming from these rivers. Over the centuries the rivers have had to relinquish much of their space, and they are now squeezed between dikes which in recent decades have become ever higher. The land behind the dikes has sunk in many places. Demographic trends and economic growth have upped the ante enormously. A flood would have huge consequences: both the emotional and economic damage would be devastating. And climate change is expected to compound the problem. The imminent threat of flooding in 1993 and 1995 showed that the problem must not be underestimated.

The Dutch government has decided both to ensure that flood protection has reached statutory levels by 2015 and to improve spatial quality in the riverine area. Given that design river discharges are expected to increase, the government wishes to achieve the required safety levels by applying measures that prevent a further increase in design high water levels. This is a shift from dike reinforcement to river relief, and will involve measures on both sides of the dikes. Dikes will only be improved where other measures are either inappropriate or unaffordable. Some restructuring of the riverine area is, however, unavoidable.

Climate change in particular means that investment will be needed to ensure the safety of the riverine area in the future too.

Objective
The Dutch government seeks to achieve two interrelated objectives:
1 To bring flood protection for the riverine area to the required level;
2 To contribute to improving the spatial quality of the riverine area.
Guaranteeing safety is the main objective; improving spatial quality is the secondary objective.

Safety
By no later than 2015, the safety level in the riverine area around the various branches of the Rhine should be in accordance with a design discharge of 16,000 m³/s at Lobith (entrance point of river Rhine in The Netherlands). By the same year, the safety level in the section of the Maas below Hedikhuizen should be in accordance with a design discharge of 3,800 m³/s at Borgharen. An additional influx from the tributaries raises the design discharge for the IJssel by a further 250 m³/s.

Further increases in river discharges and in sea level are expected and must be factored into measures for achieving the required safety levels. Future spatial developments must not form an obstacle in taking the necessary measures.

Solution
While ongoing dyke reinforcement will certainly reduce the risks, any flooding that does occur will have an even greater impact: more water will flow onto the low-lying land behind these very dykes. If the Netherlands is to be a safe, comfortable and pleasant home for all its inhabitants, the trend needs to be reversed, and the Dutch government’s plan to make more room for the river provides the solution. This involves elevating safety levels to ensure flood protection for residents and the land areas behind the dykes. Under the Room for the River program, the river will have more room at more than thirty locations. The programme’s key objective is to complete flood protection measures by 2015, while simultaneously enhancing overall environmental quality in the river region.

A range of measures is being implemented to create more room for the river while reducing high water levels. This will include lowering floodplains, relocating dykes further inland, lowering river groins, and deepening summer beds. Dykes will only be reinforced where other options are either too costly or below optimal requirements.

Picture 4, The Dutch Delta and the Room for the river plan, shows more than 30 locations for improvement. For the realization of the plan a budget of some 2.3 billion EURO is available.

Implementation
For the implementation of the Room for the River program it can be chosen from a pallet of measures, such as shown below. Via early involvement of the contractors, made possible using Plan, Design and Construct Contracts, realistic solutions are generated in respect of finance, planning and technical execution and that meet the criteria set forth in the Room for the River Program.

Picture 5, A Menu Of Measures.

The Dutch Government has selected Van Oord as a contractor  for the realization of part of the Room for the River Program.

Van Oord has amongst others been involved in the execution of the following projects: Depoldering of the Overdiepse Polder (see also the next paragraph), Floodplain Excavation Munnikenland and Floodplain Excavation Meinerswijk, for details see the sources used.

In its search for solutions that help keeping the feet of the Dutch people dry, the Dutch Government can rely on support from the so called Taskforce Deltatechnology.

In the Taskforce reputable Engineering and Contracting companies are united, such as Van Oord.

Example Depoldering of the Overdiepse Polder
In the Overdiepse Polder, in the Dutch Province of Noord-Brabant, Van Oord carried out a unique, innovative project to solve flooding problems in the polder.

The area is assigned as an overspill area by the national government, the local farmers needed protection against the water. Building mounds (terps) offers a sound solution: it allows some of the farmers to continue working in this area and essentially put the farms on higher ground, where it’s safe. The dike along the river Bergsche Maas is lowered so that excess water can run into the polder when the river rises. Van Oord constructed the new primary flood defence, the areas for the mounds, the lowering of the old dike, and a number of civil engineering works. One of these is a pumping station, which will pump away the water if the area floods. This unique project involved many innovations that have made it an appealing project for delegations from countries around the world, such as: Azerbaijan, China, France, Taiwan, and Japan. All of these countries have flooding problems and are curious to see how things are being solved in The Netherlands.

Facts and figures:
What: The renewed Overdiepse Polder will be available for sustainable agricultural land use, and there will be more space for managing water levels in the river. This is an outstanding project because of the mounds plan; the polder's residents and farmers jointly sought information about the development during an early planning stage and provided the final solution.
Client: Waterschap Brabantse Delta
Completion date: Late 2015
Goal: Lowering the water level of the river by 27 centimetres in anticipation of flooding

Concluding
Every area with the risk of flooding needs depending on factors such as: water levels, activities, environmental parameters and so on, a tailor made solution. The Dutch delta with its dense population provides for much of the challenges that might be faced and the experience and solutions applied there might be as well used in the Russian Environment.

Anko Bos, Branch Manager of Van Oord in Russia