In order to develop the system's framework, the 4R criteria of resiliency are utilized. The proposed framework is a parametric approach based on the characteristics of the WWTPs that are effective on flood consequences. Therefore, at the first step, a list of quantifiable factors that are related to the performance and resiliency of WWTPs in times of flooding is prepared (Karamouz & Nazif 2013; Zahmatkesh 2014; Karamouz & Zahmatkesh 2016). These factors are from different data types, such as hydrological, social, economic, and technical. Then, actual values for the identified factors are collected. The considered factors (sub-criteria) are presented in Table 1. Based on the definition of the 4Rs of resiliency, it also determines partitioning resiliency into four different criteria, and which sub-criterion belongs to which criteria.
Different sub-criteria for WWTPs to quantify flood resiliency
| Resiliency term (criteria) . | ID . | Sub-criteria description . | Unit . |
|---|---|---|---|
| Rapidity | Ra1 | Hurricane flood elevation (based on North American Vertical Datum of 1988 (NAVD88)) | ft |
| Ra2 | Adverse environmental impacts on the surrounding area (due to treatment failure because of flooding) | – | |
| Ra3a | Plant design capacity (a function of the plant users) | MGDb | |
| Ra4 | Post-stress recovery (refers to any disaster management plan after the flood disaster) | hour | |
| Ra5 | Population served (number of residents that are served by the plant) | # | |
| Robustness | Ro1 | Additional load in time of flooding (the difference between WWTP capacity for the total maximum wet and dry weather flow. Maximum wet weather flow is the maximum flow received during any 24 hour period. Maximum dry weather flow is the maximum daily flow during periods without rainfall) | MGD |
| Ro2 | Critical flood elevation (100-year flood elevation +30 inches for expected sea level rise by the 2050s, which is determined based on the Federal Emergency Management Agency's new advisory base flood elevation maps for a 100-year flood event, was selected as the baseline for the analysis) | ft | |
| Ro3 | Maximum inundation depth (due to the flat terrain of the plant, several areas may be flooded by up to this value of water during the critical flood event) | ft | |
| Ro4a | Percent of not-at-risk equipment (percent of plant items that are not at risk of damage during flood) | % | |
| Ro5 | DMR violations (the percentage of discharge monitoring reports that resulted in effluent violations. During minimal levels of stress, the DMR violation percentages are indicative of how well each treatment plant can cope with daily operational stresses) | % | |
| Ro6 | Damage cost from the most severe historical hurricane (without flood protection for the plant) | $ | |
| Resourcefulness | Rs1a | Number of plant technical staff | # |
| Rs2a | Availability of dewatering facilities (facilities to drain sludge to decrease 90% of its liquid volume) | – | |
| Rs3 | Total risk avoided for every single dollar spent over 50 years | $ | |
| Redundancy | Rd1 | Existence of underground tunnel systems | – |
| Rd2 | Availability of WWTPs in the neighboring areas (distance from the closest WWTP) | ft | |
| Rd3a | On-site storage (volume of lakes in the WWTP's zone) | ft3 |
| Resiliency term (criteria) . | ID . | Sub-criteria description . | Unit . |
|---|---|---|---|
| Rapidity | Ra1 | Hurricane flood elevation (based on North American Vertical Datum of 1988 (NAVD88)) | ft |
| Ra2 | Adverse environmental impacts on the surrounding area (due to treatment failure because of flooding) | – | |
| Ra3a | Plant design capacity (a function of the plant users) | MGDb | |
| Ra4 | Post-stress recovery (refers to any disaster management plan after the flood disaster) | hour | |
| Ra5 | Population served (number of residents that are served by the plant) | # | |
| Robustness | Ro1 | Additional load in time of flooding (the difference between WWTP capacity for the total maximum wet and dry weather flow. Maximum wet weather flow is the maximum flow received during any 24 hour period. Maximum dry weather flow is the maximum daily flow during periods without rainfall) | MGD |
| Ro2 | Critical flood elevation (100-year flood elevation +30 inches for expected sea level rise by the 2050s, which is determined based on the Federal Emergency Management Agency's new advisory base flood elevation maps for a 100-year flood event, was selected as the baseline for the analysis) | ft | |
| Ro3 | Maximum inundation depth (due to the flat terrain of the plant, several areas may be flooded by up to this value of water during the critical flood event) | ft | |
| Ro4a | Percent of not-at-risk equipment (percent of plant items that are not at risk of damage during flood) | % | |
| Ro5 | DMR violations (the percentage of discharge monitoring reports that resulted in effluent violations. During minimal levels of stress, the DMR violation percentages are indicative of how well each treatment plant can cope with daily operational stresses) | % | |
| Ro6 | Damage cost from the most severe historical hurricane (without flood protection for the plant) | $ | |
| Resourcefulness | Rs1a | Number of plant technical staff | # |
| Rs2a | Availability of dewatering facilities (facilities to drain sludge to decrease 90% of its liquid volume) | – | |
| Rs3 | Total risk avoided for every single dollar spent over 50 years | $ | |
| Redundancy | Rd1 | Existence of underground tunnel systems | – |
| Rd2 | Availability of WWTPs in the neighboring areas (distance from the closest WWTP) | ft | |
| Rd3a | On-site storage (volume of lakes in the WWTP's zone) | ft3 |
aSub-criteria with investment potential to improve.
bMillion gallons per day.
1 ft = 0.3048 m, 1 gallon = 3.78 litres, 1 inch = 2.54 cm.