Main characteristics

• temporary channel flow harvested either (a) using natural flooding or diverting spate flow from rivers and large gullies; or (b) impounding water within channel bed / valley floor
• stabilization of river bed to avoid scour
• spur diversions, channeling of water or cross riverbed dams (often breachable) in seasonal stream or river; dam materials are earth, stone, brushwood or reinforced material (gabions, rock masonry, concrete) or combinations; runoff stored in soil over whole planted area
• large distant catchment (may be several kilometers)
• size 2 to: 50 km²
• catchment: application area ratio 100:1 – 10,000:1
• defined water usage rules
• provision for overflow of excess water: through central spillway or two lateral spillways or by capacity to breach (e.g. temporary earth structures)
• (traditional) engineering skills needed
• in combination with groundwater recharge and subsequent use leading to highly productive systems
• often ‘self-fertilizing’ through sediment build-up
• no control over catchment area because located outside farm boundaries 

Main benefits

• FloodWH uses water which upstream users often do not require or cannot retain, as rainfall during the periods of water harvesting is abundant. FloodWH is therefore a good opportunity to provide low cost water that is not needed upstream.
• Permits cultivation of large areas.
• Floods, and thus associated negative impacts such as erosion downstream, can be partially controlled.
• Deposition of sediments carried with the floodwater builds up nutrient-rich soils.
• Excess floodwater – not immediately used for production – contributes to aquifer recharge.

Main disadvantages

• FloodWH technologies are risk-prone due to the high unpredictability in numbers, volumes and timings of floods.
• Occasionally high floods can destroy water diversion structures.
• High sediment loads clog intake structures and diversion channels; diversion structures have to be repaired or replaced regularly, often each season, and require considerable labour for maintenance.
• Floods diverted sometimes lead to negative impacts on downstream ecosystems.

(Mekdaschi & Liniger 2013, Critchley & Siegert 1991, African Development Bank 2009, Van Steenbergen et al. 2010, Liniger et al. 2011, Critchley & Gowing 2012, Oweis et al. 2012)