1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Book project: Making sense of research for sustainable land management (GLUES)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

University of Oldenburg (University of Oldenburg) - Germany

1.3 Conditions regarding the use of data documented through WOCAT

When were the data compiled (in the field)?

10/06/2015

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

2.1 Short description of the Technology

Definition of the Technology:

Water retaining polders to reduce flood risk due to heavy rainfall or runoff at high tide in embanked coastal lowlands. Delineation of the retention area and land use within the retention area was developed in a participatory process with local experts.

2.2 Detailed description of the Technology

Description:

In the 19th and 20th century land was reclaimed from the sea to make use of the exposed fertile soils for agriculture through a process known as ‘impoldering’. The reclaimed land is now characterized by intensive grazing and cropland. This is a region where agriculture is the most important form of land use. However, the land needs to be regularly drained. Given the expected increase in precipitation in winter due to climate change, the corresponding increase in freshwater discharge needs to be managed. Furthermore, the periods when natural discharge into the sea oc-curs are likely to decrease – because of rising sea levels also caused by climate change. Consequently, in winter and spring, greater quantities of freshwater will need to be pumped into the sea rather than discharged naturally at the low or ‘ebb’ tide. Specially embanked water retention polders will be required to temporarily impound water as part of a multifunctional approach to coastal zone management.

Purpose of the Technology: These retention polders could be a cost-effective alternative to expensive invest-ments in extra pumping capacities to prevent submergence of low-lying cultivated areas. The primary aim is to restrict floods to the retention polders when the drain-age network is overburdened and cannot deal with the predicted extra demands in the future. The high evapotranspiration from the open waterbody, and the reeds growing within, will also help with reducing the amount of water. During dry sum-mers, the water in the retention polder could also be put to creative use as a source of irrigation. Another potential advantage is that subsurface saltwater intrusion in the region could be prevented by the freshwater-filled polders. During extreme storm surges and in the rare case of breaches in the sea wall, the retention polders would serve as an extra line of defence by holding seawater.

Establishment / maintenance activities and inputs: An embankment enclosing approx. 500 ha will be able to store up to 2,500,000 m³ of water. This will improve the drainage of an area of approx. 49,000 ha. The invest-ment for building this water retention area is high – but for the reasons stated it serves a necessary purpose at a cost which is lower than the alternative – increased pumped drainage installations. Maintenance costs will be lower than the drainage alternative as only the integrity of the embankment needs to be monitored regularly. Currently, agricultural land use within the polders is adapted to higher water levels and occasional flooding. Within the embanked area there will be a change from the current use of mainly crop land to extensive grazing, open water and reed stands.

Natural / human environment: Some parts within the retention polder will be used for agricultural purposes, while the wetter parts will be set aside. In these latter sections, undisturbed natural regen-eration will take place. A landscape comprising various different elements, without any extreme forms of intensive land use such as large areas of monocultures will be the result. Thus requirements for agricultural use and tourism will be addressed.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

2.6 Date of implementation

If precise year is not known, indicate approximate date:

• 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• during experiments/ research
• through projects/ external interventions

3.2 Current land use type(s) where the Technology is applied

Comments:

Major land use problems (compiler’s opinion): Flood events and droughts may substantially disrupt the contemporary land use in the future and lead to higher drainage costs and higher economic risks for agricultural production. This may reduce the ecological and economic viability of the current intensive and highly productive land use under a changing climate.

Major land use problems (land users’ perception): There is no awareness of risks due to climate change in the land users point of view.

Cut-and-carry/ zero grazing: cows for milk

Improved pasture: cattle for milk and meat

Future (final) land use (after implementation of SLM Technology): Other: Oo: Other: wastelands, deserts, glaciers, swamps, recreation areas, etc

Constraints of infrastructure network (roads, railways, pipe lines, power lines): needs to be adapted to regular flooding

Constraints of recreation (landscape is used for recreation and tourism ): change in landscape due to retention area

Constraints of nature conservation area (protected sites): wetter conditions in retention area

If land use has changed due to the implementation of the Technology, indicate land use before implementation of the Technology:

Mixed: Mp: Agro-pastoralism

3.3 Further information about land use

Comments:

Water supply: rainfed, mixed rainfed - irrigated

Number of growing seasons per year:

• 1

Specify:

Longest growing period in days: 240Longest growing period from month to month: March to October

Livestock density (if relevant):

> 100 LU /km2

3.4 SLM group to which the Technology belongs

• surface water management (spring, river, lakes, sea)
• wetland protection/ management

• Flood prevention

3.5 Spread of the Technology

Comments:

Total area covered by the SLM Technology is 33.7 m2.

3.6 SLM measures comprising the Technology

Comments:

Main measures: structural measures

Secondary measures: management measures

3.7 Main types of land degradation addressed by the Technology

Comments:

Main type of degradation addressed: Hs: change in quantity of surface water

Secondary types of degradation addressed: Cs: salinisation / alkalinisation, Hg: change in groundwater / aquifer level, Hq: decline of groundwater quality

Main causes of degradation: change of seasonal rainfall (Climate change, higher rainfall in winter, lower in summer), Heavy / extreme rainfall (intensity/amounts) (Heavy rainfall in winter due to climate change expected), floods (Flooding due to heavy rainfall in winter)

Secondary causes of degradation: droughts (Droughts due to less rainfall in summer (climate change)), other natural causes (avalanches, volcanic eruptions, mud flows, highly susceptible natural resources, extreme topography, etc.) specify (Sea level rise)

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

• prevent land degradation
• reduce land degradation

Comments:

Main goals: prevention of land degradation

Secondary goals: mitigation / reduction of land degradation

4.1 Technical drawing of the Technology

4.2 Technical specifications/ explanations of technical drawing

The figure shows the study region, located on the North Sea coast. The whole area is protected by a sea wall (grey). Crop fields (yellow), grasslands (green) and the drainage system (light blue) char-acterize the region. In contrast to T_GER001en and T_GER002en small water bodies (blue) surrounded by reeds (brown) act as water retention polders. Agricultural land use in some retention areas is adapted to the ground water levels and flooding frequencies. This results in parts of the retention areas being taken out of agricultural production and undisturbed development of natural habitats occurring. In other parts of the retention areas extensive grazing or reed farming will be practiced. This leads to a mosaic of different land uses in the landscape. Retention areas of 500 ha are able to store up to 2,500,000 m³ water. The height of the dams depends on the elevation of the landscape but in general a height of less than 2 m is sufficient.

Location: Krummhörn. County of Aurich, Lower Saxony

Technical knowledge required for field staff / advisors: high (To generate income in the retention area (without existing agricultural methods))

Technical knowledge required for water board: high (To build a new adapted drainage system with retention areas)

Main technical functions: control of dispersed runoff: retain / trap, control of concentrated runoff: retain / trap

Secondary technical functions: increase / maintain water stored in soil, increase of groundwater level / recharge of groundwater, spatial arrangement and diversification of land use

Dam/ pan/ pond
Height of bunds/banks/others (m): 1
Width of bunds/banks/others (m): 2
Length of bunds/banks/others (m): 13000

Construction material (earth): sand core and clay cover

Specification of dams/ pans/ ponds: Capacity 2500000m3

Catchment area: 49000ham2

Beneficial area: 49000ham2

Other specifications: size of retention area (embanked area): 500.00 ha

Change of land use type: Within the retention area the conditions are wetter than before. Therefore the agricultural land use needs to be changed to an adapted land use.

Change of land use practices / intensity level: Under the wetter conditions only a less intensive land use is possible, e.g. no crop fields but instead extensive grazing or cessation of agricultural land use.

4.3 General information regarding the calculation of inputs and costs

other/ national currency (specify):

Euro

Indicate exchange rate from USD to local currency (if relevant): 1 USD =:

0.94

4.4 Establishment activities

	Activity	Type of measure	Timing
1.	Building of dams	Structural	during winter months

4.5 Costs and inputs needed for establishment

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Labour	Dam	1.0	10000000.0	10000000.0
Equipment	Machine use	Dam	1.0	4000000.0	4000000.0
Construction material	Earth	Dam	1.0	112000.0	112000.0
Total costs for establishment of the Technology					14112000.0

Comments:

Duration of establishment phase: 3 month(s)

4.6 Maintenance/ recurrent activities

	Activity	Type of measure	Timing/ frequency
1.	Control of dams	Structural	once a year
2.	Maintenance of dams	Structural	once a year
3.	Maintenance of drainage system	Structural	once a year (mean of many years)

4.7 Costs and inputs needed for maintenance/ recurrent activities (per year)

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Labour	Dam	1.0	500.0	500.0
Equipment	Machine use	Dam	1.0	200.0	200.0
Construction material	Earth	Dam	1.0	100.0	100.0
Other	Maintenance per km ditch	Dam	1.0	2270.7	2270.7
Total costs for maintenance of the Technology					3070.7

Comments:

Machinery/ tools: digger, open truck

The main investment is based on a dam length of 13 km to build up the retention area of a size of 500 ha. The length of the drainage network for the whole watershed (retention area and the surroundings) is 1,134 km. Maintenance costs of drainage network are based on long term annual mean cost of 2,270.72 Euro per km including pumping costs.

4.8 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

The establishment costs are for the whole retention area (500 ha). The establishment period will be half a year.
Mainly the elevation in the region determines the costs as the height of the dams depend on the elevation. Typical heights are 1 m up to 2 m with a slope of 1:3.

5.1 Climate

5.2 Topography

5.3 Soils

If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil fertility is high
Soil drainage/infiltration is meidum
Soil water storage capacity is high

5.4 Water availability and quality

5.5 Biodiversity

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly common / average land users

Population density: 50-100 persons/km2

Annual population growth: < 0.5%

1% of the land users are very rich and own 1% of the land.
49% of the land users are rich and own 24% of the land.
50% of the land users are average wealthy and own 50% of the land.
and own 25% of the land.

Off-farm income specification: Many farmers do additional work in companies

5.7 Average area of land owned or leased by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• individual, not titled

Land use rights:

• individual

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Income and costs

Other socio-economic impacts

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Biodiversity: vegetation, animals

Climate and disaster risk reduction

6.2 Off-site impacts the Technology has shown

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

	Season	Type of climatic change/ extreme	How does the Technology cope with it?
annual temperature		increase	well

Climate-related extremes (disasters)

Meteorological disasters

	How does the Technology cope with it?
local rainstorm	well
local windstorm	well

Climatological disasters

	How does the Technology cope with it?
drought	well

Hydrological disasters

	How does the Technology cope with it?
general (river) flood	well

Other climate-related consequences

Other climate-related consequences

	How does the Technology cope with it?
reduced growing period	not known

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

Comments:

The benefits will be visible in an longer time frame. There will be benefits of the investments when considering sea level rise in the upcoming 100 years.

6.5 Adoption of the Technology

Comments:

Comments on spontaneous adoption: The SLM Technology is not implemented by land users but needs to be implemented in spatial planning of the federal state. We expect that there is a chance for implementation.

There is a strong trend towards spontaneous adoption of the Technology

Comments on adoption trend: The SLM Technology was developed together with regional experts. It seems that the ideas developed, merge more often in their recent discussion and an implementation is likely.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
The retention area will supplement the drainage of the arable fields and pastures outside the retention area How can they be sustained / enhanced? Combine with other technical solutions for protection against flooding.

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Prevention of flooding during strong rainfalls and possibility to irrigate during dry periods How can they be sustained / enhanced? The larger the retention areas are the more water can be stored
Prevention of salt water intrusion in the region How can they be sustained / enhanced? Fresh water in the retention areas prevents saline ground water from intrusion. Build polders in areas where saline ground water intrudes.
Endangered species might obtain new habitats in the retention area How can they be sustained / enhanced? Extensive land use can help to optimize the habitats for endan-gered species and increase attractiveness for tourism.
Through investments in building retention polders the very ex-pensive strengthening of the existing drainage system is no longer necessary. How can they be sustained / enhanced? By increasing the attractiveness for tourism alternative benefits for land owner can be generated.
Multi-functional land use in the catchment and in the retention area How can they be sustained / enhanced? Support farmers with land in the retention area (e.g. financially or with additional agricultural land outside the retention area). Sup-port discussions between farmers’ associations and nature con-servation agencies.

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view	How can they be overcome?
The retention polders will change the landscape and this may reduce the value of the region for tourism	Include tourist concerns within the retention area (accessibility, information, attractiveness)
Endangered species might lose habitats when building up the retention polders	Do not build a retention area where endangered species live
Loss of livelihoods	Retention areas should be planned for parts of the landscape without settlements

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view	How can they be overcome?
Loss of land for agricultural production	Create retention polders where the productivity is already low. Encourage alternative land use (for example reed production) in the retention polders.
High water levels (especially with changing levels) may generate high emissions of greenhouse gases.	Ground water levels should kept stable near to the soil surface.
Retention area is probably too small if pessimistic sea level rise predictions come true.	Increase size of retention polders.

7.2 References to available publications

Title, author, year, ISBN:

http://www.comtess.uni-oldenburg.de/

7.3 Links to relevant information which is available online

Title/ description:

http://www.comtess.uni-oldenburg.de/