1.2 Coordonnées des personnes-ressources et des institutions impliquées dans l'évaluation et la documentation de la Technologie

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

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

Nom du projet qui a facilité la documentation/ l'évaluation de la Technologie (si pertinent)

Sustainable Coastal Land Management (COMTESS / GLUES)

Nom du ou des institutions qui ont facilité la documentation/ l'évaluation de la Technologie (si pertinent)

University of Oldenburg (University of Oldenburg) - Allemagne

1.3 Conditions relatives à l'utilisation par WOCAT des données documentées

Le compilateur et la(les) personne(s) ressource(s) acceptent les conditions relatives à l'utilisation par WOCAT des données documentées:

Oui

1.5 Référence au(x) Questionnaires sur les Approches de GDT (documentées au moyen de WOCAT)

2.1 Courte description de la Technologie

Définition de la Technologie:

Water retaining polders to reduce flood risk from heavy rainfall or runoff at high tide in coastal lowlands. Alternative production systems will be viable within thesepolders.

2.2 Description détaillée de la Technologie

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. 3,000 ha will be able to store up to 25,000,000 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. Agricultural land use within the polders is adapted to higher water levels and occa-sional flooding.

Natural / human environment: However within the proposed retention polders – the areas enclosed by the em-bankment - a change from the current intensive grazing for dairy farming and cropland to extensive grazing, open waters and wetlands covered with reeds will take place. The reeds can be harvested for their commercial value as biomass for renewable energy generation, or for other applications (e.g. thatching of roofs or industrial raw material). According to recent investigations, natural reeds growing in brackish water produce as much biomass as maize cultivated for biogas use. In con-trast to maize, no investments in tillage, fertilizer or biocides are necessary for these naturally growing reed stands. Thus the proposed land use provides an economic alternative to the current production system.

2.3 Photos de la Technologie

2.5 Pays/ région/ lieux où la Technologie a été appliquée et qui sont couverts par cette évaluation

2.6 Date de mise en œuvre de la Technologie

Si l'année précise est inconnue, indiquez la date approximative: :

• il y a entre 10-50 ans

2.7 Introduction de la Technologie

Spécifiez comment la Technologie a été introduite: :

• au cours d'expérimentations / de recherches
• par le biais de projets/ d'interventions extérieures

3.2 Type(s) actuel(s) d'utilisation des terres, là où la Technologie est appliquée

Les divers types d'utilisation des terres au sein du même unité de terrain: :

Oui

Précisez l'utilisation mixte des terres (cultures/ pâturages/ arbres):

• Agropastoralisme (y compris les systèmes culture-élevage intégrés)

Commentaires:

Major land use problems (compiler’s opinion): Flood events and droughts may substantially disrupt the current land use system in the future and lead to higher drainage costs and higher economic risks for agricultural production. This will 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.

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

Livestock density: > 100 LU /km2

3.3 Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

Est-ce que l’utilisation des terres a changé en raison de la mise en œuvre de la Technologie ?

• Non (Passez à la question 3.4)

Commentaires:

Mixed: Mp: Agro-pastoralism

3.4 Approvisionnement en eau

Commentaires:

Water supply: rainfed, rainfed, mixed rainfed - irrigated

3.5 Groupe de GDT auquel appartient la Technologie

• dérivation et drainage de l'eau
• gestion des eaux de surface (sources, rivières, lacs, mers)

3.6 Mesures de GDT constituant la Technologie

Commentaires:

Main measures: structural measures

Secondary measures: management measures

3.7 Principaux types de dégradation des terres traités par la Technologie

Commentaires:

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 Prévention, réduction de la dégradation ou réhabilitation des terres dégradées

Spécifiez l'objectif de la Technologie au regard de la dégradation des terres:

• prévenir la dégradation des terres
• réduire la dégradation des terres

Commentaires:

Main goals: prevention of land degradation

Secondary goals: mitigation / reduction of land degradation

4.1 Dessin technique de la Technologie

4.2 Informations générales sur le calcul des intrants et des coûts

autre/ monnaie nationale (précisez):

Euro

Indiquez le taux de change des USD en devise locale, le cas échéant (p.ex. 1 USD = 79.9 réal brésilien): 1 USD = :

0,94

4.3 Activités de mise en place/ d'établissement

	Activité	Calendrier des activités (saisonnier)
1.	Building of dams	during winter months

Commentaires:

Labour medium: 1 person 1 day, 1m dam, 700USD
Machine hours: 8h, 1m dam, 300 USD
Earth: 10000 M3 (Sand), whole retention area, 22000 USD
Earth: 23000 M3 (Klei), whole retention area, 53000 USD

4.4 Coûts et intrants nécessaires à la mise en place

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% du coût supporté par les exploitants des terres
Main d'œuvre	Labour		1,0	21000000,0	21000000,0
Equipements	Machine use		1,0	9000000,0	9000000,0
Matériaux de construction				750000,0
Coût total de mise en place de la Technologie					30000000,0
Coût total de mise en place de la Technologie en dollars américains (USD)					31914893,62

Commentaires:

Duration of establishment phase: 3 month(s)

4.5 Activités d'entretien/ récurrentes

	Activité	Calendrier/ fréquence
1.	Control of dams	once a year
2.	Maintenance of dams	once a year
3.	Maintenance of drainage system	once a year

4.6 Coûts et intrants nécessaires aux activités d'entretien/ récurrentes (par an)

	Spécifiez les intrants	Unité	Quantité	Coûts par unité	Coût total par intrant	% du coût supporté par les exploitants des terres
Main d'œuvre	Labour			800,0
Equipements	Machine use			300,0
Matériaux de construction	Earth			100,0

Commentaires:

Machinery/ tools: digger, open truck

The establishment costs are for a dam length of 30 km and the enclosed retention area of 3,000 ha. The establishment period will be half a year. The slope in the region determines the costs as the height of the embankments depend on this. Typical heights are from 1 m up to 2 m with a slope of 1:3. . The length of the drainage network for the whole watershed (retention area and the surroundings) is 1,134 km. Maintenance costs of the drainage network are based on long term annual mean cost of 2,270.70 Euro per km including pumping costs. The maintenance cost for the whole retention area will amount to a total of US$ 2,576,200.00.

5.1 Climat

5.2 Topographie

5.3 Sols

Si disponible, joignez une description complète du sol ou précisez les informations disponibles, par ex., type de sol, pH/ acidité du sol, capacité d'échange cationique, azote, salinité, etc.

Soil fertility is very high
Soil drainage/infiltration is medium
Soil water storage capacity high

5.4 Disponibilité et qualité de l'eau

5.5 Biodiversité

5.6 Caractéristiques des exploitants des terres appliquant la Technologie

Indiquez toute autre caractéristique pertinente des exploitants des terres:

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.
50% 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 industry or servicing sector

5.7 Superficie moyenne des terres utilisées par les exploitants des terres appliquant la Technologie

5.8 Propriété foncière, droits d’utilisation des terres et de l'eau

Propriété foncière:

• individu, sans titre de propriété

Droits d’utilisation des terres:

• individuel

5.9 Accès aux services et aux infrastructures

6.1 Impacts sur site que la Technologie a montrés

Impacts socio-économiques

Production

Disponibilité et qualité de l'eau

Revenus et coûts

Autres impacts socio-économiques

Impacts socioculturels

Impacts écologiques

Cycle de l'eau/ ruissellement

Sols

Biodiversité: végétale, animale

Réduction des risques de catastrophe et des risques climatiques

6.2 Impacts hors site que la Technologie a montrés

6.3 Exposition et sensibilité de la Technologie aux changements progressifs et aux évènements extrêmes/catastrophes liés au climat (telles que perçues par les exploitants des terres)

Changements climatiques progressifs

Changements climatiques progressifs

	Saison	Augmentation ou diminution	Comment la Technologie fait-elle face à cela?
températures annuelles		augmente	bien

Extrêmes climatiques (catastrophes)

Catastrophes météorologiques

	Comment la Technologie fait-elle face à cela?
pluie torrentielle locale	bien
tempête de vent locale	bien

Catastrophes climatiques

	Comment la Technologie fait-elle face à cela?
sécheresse	bien

Catastrophes hydrologiques

	Comment la Technologie fait-elle face à cela?
inondation générale (rivière)	bien

Autres conséquences liées au climat

Autres conséquences liées au climat

	Comment la Technologie fait-elle face à cela?
réduction de la période de croissance	pas connu

6.4 Analyse coûts-bénéfices

Quels sont les bénéfices comparativement aux coûts de mise en place (du point de vue des exploitants des terres)?

Quels sont les bénéfices comparativement aux coûts d'entretien récurrents (du point de vue des exploitants des terres)?

Commentaires:

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

6.5 Adoption de la Technologie

Commentaires:

Comments on spontaneous adoption: The SLM Technology is not implemented by local land users but this SLM technology needs to be implemented by spatial planning of the county / federal state.

There is a little trend towards spontaneous adoption of the Technology

Comments on adoption trend: The SLM Technology is not yet implemented by land users but first it needs to be considered in spatial planning of the county and the federal state. Land users and local experts showed during participatory workshops that there may be a chance for implementation.

6.7 Points forts/ avantages/ possibilités de la Technologie

Points forts/ avantages/ possibilités du point de vue de l'exploitant des terres
The retention area will support 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 (including strengthening of the ditch system and in-creasing pumping capacity).

Points forts/ avantages/ possibilités du point de vue du compilateur ou d'une autre personne ressource clé
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 polders 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 endangered species and increase attractiveness for tourism.
Through investments in building retention areas the very expensive strengthening of the existing drainage system is not necessary anymore How can they be sustained / enhanced? By increasing the attractivity for touristic use in the retention area benefits for land owner can be generated and the probability to build up retention areas instead of strengthening the existing drainage system is increased.

6.8 Faiblesses/ inconvénients/ risques de la Technologie et moyens de les surmonter

Faiblesses/ inconvénients/ risques du point de vue de l’exploitant des terres	Comment peuvent-ils être surmontés?
Retention polders in an important tourism region will change the landscape and this may reduce the value of the region for tourism.	Include tourism concerns in the retention area (access, infor-mation, attractiveness).
Loss of land for agricultural production (highly productive arable land)	Establish retention area in low elevated parts, where there is not a high interest for agricultural production.
Endangered species might lose habitats when building up the retention area	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.

Faiblesses/ inconvénients/ risques du point de vue du compilateur ou d'une autre personne ressource clé	Comment peuvent-ils être surmontés?
High water levels (especially with changing water levels) may generate high emission of greenhouse gas	Ground water levels should kept stable near to the soil surface.

7.1 Méthodes/ sources d'information

7.2 Références des publications disponibles

Titre, auteur, année, ISBN:

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