Land Set-Aside for Flood Risk Management
Content Table
What is land-set aside?
This term is largely undefined in flood risk management. The term is often used in an former European Union progamme where it meant that farmers were paid to reduce their production capacity in order to re-balance the food market.
In water management this term could indicate that farmers are paid to allow their land to function as water storage area in times with excess water levels. In the Netherlands farmers are principally entitled to a minimum level of safety against inundation from water courses. Usually this safety level is set at 1:10, which means that inundation of their lands is only allowed during events with a return period of more than 10 years. When farmers agree with a lower level of safety (which is in effect a water storage measure) they are often financially compensated. This could be seen as land-set aside for water storage.
Mitigation Strategy
The Mitigation Strategy of the measure Land set aside refers to flood prevention and environmental protection also.
Flood protection can be achieved by:
- Delay and infiltration of surface run off (high roughness of fallow land);
- Increase the possibility of infiltration by regeneration of soil compaction and avoidance of soil silting (usually more intense and multi rootsystem);
- Accumulation of litter and humus layers;
- The hydrologic-hydraulic effect depends on the fouling (weed fallow, bush fallow, sowing), soil condition at the time of land set aside (compression, water conductivity), season and age of the land set aside.
Environmental protection by:
- Support structural diversity and biodiversity in agricultural landscapes,
- Improving habitat functions for animal and plant species which are characteristic for the field corridors (function as part of habitat, as a food source, breeding site, as a retreat space),
- Function as catching sediment, filtering and buffering of nutrients and toxic input,
- Bioclimatic and clean air balancing function (cold air generation, filtering) of air pollutants,
- Appreciation of the landscape and increase of the effectiveness of landscape experience,
- The nature conservation importance of fallow land varies depending on the land set-aside duration (permanent fallow or rotation fallow), the site conditions (marginal locations, highly productive sites), the previous use, the date of land set-aside within the crop rotation and follow use (no use or only grazing).
Cons
- Increased risk of erosion at successively fallow land and spring sown fallow land in the first years,
- Risk of nitrate leaching in fallow with high N mineralization (loess loam, disposing loam) as long annuelle plants are dominating and the diaspore input of perennial species is low,
- Heightened risk of N mineralization in changing longstanding set aside
Performance Drawbacks
Introduction of land set-aside:
- The land set-aside should be performed for different durations (for example Segetalvegetation for 1-3 years, 3-7 years for farmland birds),
- If possible, small-area distribution of fallow land should be introduced (increasing the boundary density),
- Preference creation of rotating fallow land, which are as evenly distributed in the used area,
- Size of at least one to five hectares if fallow land,
- Establishing a buffer for sensitive habitat and/ or as a supplement and networking of existing biotopes,
- Reducing the use of manure and restricting pesticides at the year of implementation the land set-aside to reduce the risk of nitrate leaching and support the succession,
- If possible, it should be preferred succession instead of reseeding,
- Targeted greening by reseeding only if inadequate succession and increased risk of erosion (undersown crops recently grown culture, possible use of seed out of the area without legume seed portion).
Cultivation:
- If needed, made make multi-annual care of scrubland areas, or alternatively make multi-annual mowing or mulching from October to February to prevent scrub encroachment,
- Choice of a late mowing time if possible in July (Observation of bird breeding season, stages of development of insects);
- mowing in sections and at different times (creating a small-scale mosaic of different stages of development),
- No use or restriction of fertilizers and pesticides;
- Prevention of soil compaction;
- Cutting height no lower than 20 cm (protection of amphibians, reptiles, breeding places);
- Leave of several meter-wide strip of fallow land in very large crop fields at the end of the land set aside period;
- Possible choice of a subsequent crop, which can absorb high quantities of nitrate (for example oilseed rape).
Time to take effect
In the short term to medium term.
Costs
- Sowing and seed costs,
- Possible costs due to reducing harvest,
- Costs for reducing scrub encroachment.
A cost benefit analysis has to be done separately for each individual project. A possible procedure and the coast range for alternative solutions you will find here (link).
References
SIEKER, F. (2007): Maßnahmensteckbrief "Umwandlung von Acker in extensives Grünland", In: INSTITUT FÜR WASSERWIRTSCHAFT, HYDROLOGIE UND LANDWIRTSCHAFTLICHEN WASSERBAU (2007): Abschlussbericht zum Forschungsprojekt "Vorbeugender Hochwasserschutz durch Wasserrückhalt in der Fläche unter besonderer Berücksichtigung naturschutzfachlicher Aspekte - am Beispiel des Flusseinzugsgebietes der Mulde."
Links
Chamber of Agriculture, Lower Saxony 
