Sanitation in Flood Prone Areas

In flood prone areas, it is important to adjust sanitation solutions, to avoid the health risks associated with flooding or overflowing pits and septic tanks, causing the release of wastewater and faecal sludge into the environment. Also, flood resilient sanitation infrastructure prevents damage due to flooding, and ensures sanitation services can continue to be used during flood events.

The main aim is to prevent rainwater from submerging the equipment (raised floors, non-return valves, etc.), to reinforce the resistance of the equipment and to limit the infiltration of wastewater near water tables (watertight pits, urine diversion, etc.).

Key Actions

• Step 1: Evaluating the flooding risk.

Characterize the flood risk by collecting the following data:the area affected by flooding (linked to topography)

• the intensity of flooding (shallow or deep water? slow-moving or fast-moving flood water?)
• the frequency of the flooding event
• the duration of the event.

The aim is to establish a zoning of the territory, distinguishing between areas that are safe for sanitation systems, and those where more or less extensive flood protection measures will be required.

• Step 2: Designing or adapting sanitation systems to withstand flooding

The aim here is to choose sanitation systems which can be operated without interruption, and which do not risk discharging effluentEffluentGeneral term for a liquid that leaves a technology, typically after blackwater or sludge has undergone solids separation or some other type of treatment. Effluent originates at either a collection and storage or a (semi-) centralised treatment technology. Depending on the type… into the environment.
The SPHERE standards recommend "making the excretaExcretaRefers to human excrements consisting of urine and faeces. containment infrastructure watertight to minimise groundwaterGroundwaterWater that is located beneath the earth’s surface. contamination" or "building toilets or septicSepticDescribes the conditions under which putrefaction and anaerobic digestion take place. tanks raised".
Different options should be considered:

• Raising toilets and pits above the highest level of floodwater;
• Reinforcing the walls of latrineLatrineA sanitation facility used for urination and defecation including a 'user interface' and an 'onsite storage pit'. Often interchangeably referred to as toilet. pits (lining them with erosion-resistant materials);
• Waterproofing sludgeSludgeMixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies,… and wastewaterWastewaterUsed water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration. containment facilities where they cannot be raised above the maximum flood level;
• Limiting the risk of effluentEffluentGeneral term for a liquid that leaves a technology, typically after blackwater or sludge has undergone solids separation or some other type of treatment. Effluent originates at either a collection and storage or a (semi-) centralised treatment technology. Depending on the type… infiltrating the soil by separating urineUrineThe liquid produced by the body to rid itself of nitrogen in the form of urea and other waste products. In this context, the urine product refers to pure urine that is not mixed with faeces or water. Depending on diet, human urine collected from one person during one year… from feces (UDDT: Urine-Diverting Dry Toilets);
• Installing non-return valves on septicSepticDescribes the conditions under which putrefaction and anaerobic digestion take place. tanks.

The effectiveness of all of these measures can be enhanced by designing the adaptation measures for wastewaterWastewaterUsed water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration. and storm water management together.

Step 3: Taking into account the constraints associated with technical solutions

• Additional construction costs: masonry work on pit walls, raising latrines or tanks;
•  Additional operating costs: lifting wastewaterWastewaterUsed water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration. if storage or treatment facilities are raised, more frequent emptying of pits if they are sealed;
•  Adapting technologies to people's practices: use of urine-diverting toilets, accessibility of elevated toilets for people with reduced mobility, etc.
•  Equipment maintenance capabilities: ability to ensure regular emptying of watertight pits, maintenance of urine-diverting latrines, etc.

Relevance/Importance

Climate change and urbanization are significantly increasing the frequency of intense flooding events. Flooding of sanitation infrastructure, like latrines, toilets or treatment plants, gives rise to two types of problem:

• Disruption of sanitation services

Flooding can lead to the destruction of sanitation facilities: a frequent problem is the collapse of simple unlined pits, which are the most common type of latrineLatrineA sanitation facility used for urination and defecation including a 'user interface' and an 'onsite storage pit'. Often interchangeably referred to as toilet. in low-income countries. Disrupted sanitation services can force people into unsafe alternatives, like open defecationOpen DefecationPractice of defecating outside in the open environment., which increases public health risks.
Floods can also cause hydraulic overloading and make wastewaterWastewaterUsed water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff/stormwater, and any sewer inflow/infiltration. treatment systems (such as septicSepticDescribes the conditions under which putrefaction and anaerobic digestion take place. tanks or activated sludgeSludgeMixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies,… plants) ineffective.
Lastly, flooding can disrupt pit-emptying services (inaccessible areas, increased demand for emptying as rainwater fills the pits).

• Environmental contamination

The flooding and/or overloading of sanitation systems (including treatment plants) leads to the release of untreated effluentEffluentGeneral term for a liquid that leaves a technology, typically after blackwater or sludge has undergone solids separation or some other type of treatment. Effluent originates at either a collection and storage or a (semi-) centralised treatment technology. Depending on the type… directly into the environment. Untreated waste water and faecal sludgeSludgeMixture of solids and liquids, containing mostly excreta and water, in combination with sand, grit, metals, trash and/or various chemical compounds. A distinction can be made between faecal sludge and wastewater sludge. Faecal sludge comes from on-site sanitation technologies,… in the environment increase the public health risks and pollute the environment (potentially causing significant ecosystem degradation).

Existing flood-prone sanitation solutions can lead to higher investment costs. Also, flood-prone solutions can be considered less user friendly and require additional maintenance.