# Validating an Operational Flood Forecast Model Using Citizen Science in Hampton Roads, VA, USA
## 2 Methods  
### Citizen Science Flood Monitoring Data Collection  
_Catch the King_ is a citizen science GPS data collection effort centered in Hampton Roads, VA, which aims to map the king tide's maximum inundation extents, with the goal of validating and improving predictive models for future forecasting of increasingly pervasive nuisance flooding [16]. The aptly-named effort is the world's largest simultaneous citizen science GPS flood data collection effort, and it is aimed at benchmarking the highest astronomical tide of the year, the king tide. Certified by Guinness World Records for having 'the most contributions to an environmental survey' on the planet, _Catch the King_ was effectively publicized and promoted by the local news media, in Hampton Roads, VA [27; 32]. High citizen engagement during a king tide inundation event resulted in an average of 572 GPS-reported high water marks being recorded per minute during the hour surrounding the king tide's peak [12]. Time-stamped GPS flood extent measurements and photographic evidence were reported via the free 'Sea Level Rise' mobile application, coinciding with the king tide, observed at 13:32 UTC (Universal Time, Coordinated) on 5 November 2017, in Hampton Roads, VA. Ultimately, _Catch the King_ surveyed a total of 59,718 high water marks and 1582 photographs through 722 individual volunteers in its inaugural year [32; 33].  
Following 2017's success, _Catch the King_ was repeated during the highest astronomical tide of 2018 on 27 October. This event was less attended as it immediately followed a strong nor 'easter in a day prior, on 26 October. Still, significant response from the event's many volunteers, fueled by the local media partners' coverage leading up to the event, and 42 separate volunteer training events held all over Hampton Roads, resulted in 347 participants collecting 33,847 time-stamped GPS maximum flooding extent measurements and 458 geotagged photographs during the event [34]. There were 141 additional volunteers who collected 3881 GPS data points during the nor 'easter's peak flood period coinciding with the high tide the night before the king tide. Combined, those totals are 488 participants and 37,728 GPS points during the 2018 _Catch the King_ and nor 'easter event, with 431 of those being unique volunteers and 57 having mapped the king tide on both the 26 and 27 October 2018 [35].  
Figure 1: The SCHISM Hydrodynamic model grid used to drive the Tidewatch storm tide prediction model, and inset at right, are some example city-scale sub-grid model sub-basins for Norfolk (top) and Portsmouth (bottom) driven by SCHISM using Dirichlet boundary conditions.  
As the sea level rise and tidal flooding increasingly impact coastal Virginia, _Catch the King_ offers residents a chance to crowdsource vital information about the tides' reach. Thus, time-stamped GPS data points and photographs were collected by volunteers to effectively breadcrumb/trace the high water line by pressing the 'Save Data' button in the 'Sea Level Rise' mobile app every few steps along the water's edge during the king tide's peak in 2017 and again in 2018. Initial responses collected by the free 'Sea Level Rise' mobile application were relayed to the event's dedicated volunteers via the local news media event's volunteer coordination Facebook page. In the days following each event, several people provided additional GPS data points they collected through Esri's Geographic Information System (GIS) Collector App and crowdsourcing geo-forms through ArcGIS Online that were missing from the initial cited statistics (Figure 2). This occurred as a few volunteers noticed their data initially missing from the interactive map as it was published in the Daily Press and The Virginian-Pilot among other media sources, and were later included in the final event totals and added to the final data map [27]. These updated totals were ultimately reported back to the community a month after each inundation event in 2017 and 2018 through a volunteer thank you and data review event [16; 35].