My health unit is in the process of updating our field data entry forms in order to help with developing predictive models for our beaches. The resources available are limited, so we're trying to do everything as simply as possible. I'm hoping to get some suggestions from others about how to measure the following variables that we're unsure about.
1. Rainfall over past 48 hours - the question we're having here is whether to use the average rainfall (mm/hour) for the previous 2 days or whether we should be looking at peaks. For example, while a 5 minute torrential downpour may not greatly impact the 48 hour average, does it have enough of an impact on bacterial counts that it should be considered separately?
2. Current rainfall - what methods do people use for determining whether current rainfall (i.e. at the time of sampling) is 'low', 'medium', or 'heavy'?
3. Bather density - we have always had a measure for bather density included on our field reports, however as our samples are taken quite early in the morning, there are not usually many people on the beach and it is certainly not representative of the bather density at peak times. Have other areas encountered this problem and, if so, how was it dealt with? Have people found that bather density is of sufficient importance to bacterial counts that it needs to be measured?
4. Wave height - what methods are people using for measuring wave height, and how are they defining a wave (is it from the level of the calm water to the top of the wave, or from the bottom of the wave (which may be lower than the calm water level) to the top? Also, does anyone have a coding system for what would be considered 'low', 'medium', or 'high' waves?
Thanks in advance for all your help!
Naomi Kasman, MSc.
Health Protection Division
Public Health Branch
Community and Health Services Department
The Regional Municipality of York
17250 Yonge St. P.O. Box 147
Newmarket, ON L3Y 6Z1
Tel: 905-830-4444 x4592