Presentation is loading. Please wait.

Presentation is loading. Please wait.

Hydrological Impact of Hurricane Irene and Tropical Storm Lee in Historical Context: Is the Frequency and Magnitude of Extreme Hydrological Events Changing.

Similar presentations


Presentation on theme: "Hydrological Impact of Hurricane Irene and Tropical Storm Lee in Historical Context: Is the Frequency and Magnitude of Extreme Hydrological Events Changing."— Presentation transcript:

1 Hydrological Impact of Hurricane Irene and Tropical Storm Lee in Historical Context: Is the Frequency and Magnitude of Extreme Hydrological Events Changing in Southern New York State? Adao Matonse 1, Allan Frei 2, David Lounsbury 1 Donald Pierson 1, Mark Zion 1, and Elliot Schneiderman 1 1 New York City Environmental Protection 2 The City University of New York – Hunter College

2 2 Presentation Outline Introduction Study Area Data and Methods How Unique were Irene and Lee? The Frequency of Extreme Events in the Study Region The Magnitude of Extreme Events Implications for Hydrology Conclusions

3 3 Tannersville, photo by Sean Mahoney newsblog/2011/aug/31/focus-shifts-people-stranded-catskills- flood-waters-recede / Main Street, Margaretville destruction-photos Windham destruction-photos New Windsor washout_after_Hurricane_Irene,_New_Windsor,_NY.jpg Irene in the Catskills

4 4 Irene in the Catskills: Schoharie Creek, Prattsville Photo Immediately after Irene, Sep 1, 2011, photo by Danyell Davis, NYCDEP

5 5 Changes over Time in Frequency of Extreme Events Warner Creek, Near Stony Clove, Catskills, May 2012 Headcut incised during storms of 2011 exposing glacial till that has probably not been exposed in K yrs. Course sediment is being recruited from upstream, but channel bed now at a lower base level than prior to Irene. These sorts of fluvial geomorphological changes are related to the frequency and magnitude of extreme events, as well as human impact on channel conditions. Human impacts up- or down-stream can also play a role. Photos and geomorphological information from Danyell Davis, NYCDEP

6 6 NYSERDA funded study : Hydrology, Vulnerability and Adaptation Implications of Hurricane Irene and Tropical Storm Lee: Case Study of the Mid-Hudson Valley and Greater Catskills Regions 1.Hydrological study (this talk) 2.Impacts, Costs, and vulnerabilities 3.Adaptation and Needs Assessment

7 7 Collaborators NYCDEP: Don Pierson, Elliot Schneiderman, Mark Zion, Soni Pradhanang, Don Kent, Rajith Mukundan, Nihar Samal, Yongtai Hwang, David Lounsbury, Danyell Davis, Terry Spies, Dom Thongs, Jim Porter NYSERDA funded project on Hurricane Irene and Tropical Storm Lee: William Solecki, Simon Gruber, Robin Leichenko, Lesley Patrick, Susan Sofranko, Michael Brady

8 8 Map by David Lounsbury - NYCDEP Study Area and Station Locations

9 9 Data hourly-radar-based gridded daily 4km precipitation (NRCC) (DeGaetano and Wilks 2009) 12 precipitation gauge records (NCDC) >= 30 yrs continuous records 9 stream gauge records (USGS) >= 30 yrs continuous records, unregulated Methods Parametric (standard recurrence interval analysis) non-parametric (define extreme as >=95 th Percentile Event) Seasonal (warm season = 1 June through 31 October) Antecedent conditions (30 day precipitation prior to an extreme event) Proximity in space and time of two extreme events Data and Methods

10 10 4-Day Precipitation Contours and Recurrence Intervals Hurricane Irene (26-29 Aug., 2011) Tropical Storm Lee (5-8 Sep. 2011) Maps by David Lounsbury, NYCDEP

11 11 Precipitation-Difference Contours and Stations Irene minus Lee Irene > LeeLee > Irene Map by David Lounsbury, NYCDEP

12 12 Irene and Lee in context of historical extreme precipitation events The events of Fall 2011 were unprecedented in this region due to a combination of the magnitude of precipitation during Irene and Lee the proximity of these two events Antecedent conditions and subsequent precipitation The occurrence of two events of comparable magnitude to Irene and Lee within only 11 days of each other is highly unusual in this region 30-day total precipitation prior to Irene was large compared to other extreme events If one considers all 60-day precipitation totals on record, the fall of 2011 stands out as an unprecedented event.

13 13 Values are ranges across all stations. Percentage of Seasons During Which Extreme 4-day Precipitation Events Occur Within 12 days of each other (prior to Irene and Lee)

14 14 Frequency of Extreme Events: Non-Parametric Analysis Example from one station Ellenville 4-day Precipitation Cold SeasonWarm Season 5 highest values 95 %tile value

15 15 Non-parametric data analysis Extreme Events (All Events >= 95 percentile) Daily Precipitation Daily Streamflow Unimodal (peak in Fall) Bimodal (peaks in Spring & Fall) warm season

16 16 Number of 95%tile values per year Example from Ellenville 4-day Precipitation Cold Season max smooth value Smooth (11-yr mean) Warm Season Changes over Time in Frequency of Extreme Events:

17 17 Cold SeasonWarm Season Smooth (11-yr mean) max smooth value 1985, 2006 Changes over Time in Frequency of Extreme Events Number of 95%tile 4-d precipitation values per year all stations

18 18 Smooth (11-yr mean) max smooth value 1985, 2006 Cold SeasonWarm Season Changes over Time in Frequency of Extreme Events Number of 95%tile daily streamflow values per year all stations

19 19 Cold seasonWarm season 4-day Precipitation 1-day Streamflow Number of 95%tile values per year: all stations

20 20 Frequency analysis Daily Precipitation Daily Streamflow Warm > Cold (all events) Warm < Cold (for low return interval only)

21 21 Changes over Time in Magnitude of Flood Flows Each color is a different overlapping 30- year period starting 10 years apart One example using multiple 30-year periods annual peak flow

22 22 NOAA Climate Extremes Index (CEI) (= arithmetic average of six indicators) (accessed Sep 9, 2013) Other studies on extreme climatic events (EE) Showing increasing percentage CEI in recent years

23 23 … and projecting an increasing intensity of EE (Kunkel et al 2013, GRL)

24 24 Intergovernmental Panel on Climate Change Special Reports: SREX (2012) Climate Extreme (extreme weather or climate event): The occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends of the range of observed values of the variable.

25 25 Intergovernmental Panel on Climate Change Special Reports: SREX (2012) Projected decrease in recurrence intervals for daily precipitation equal to historical 20-year recurrence during the late 20 th Century. Different colors = different scenarios

26 26 Monier and Gao, 2013

27 27 Of changing frequency and magnitude of extreme events Bulletin 17B recommends 25-year record for flood frequency analysis Based on assumption of stationarity of climate Results show this assumption is questionable due to: Trends Hydrologic regime shifts (mean, variance) Need for a new normal Implications for Hydrology Shifts in mean Winter-flow USGS ,

28 28 Not new in water resources planning and management Is usually considered when supported by a strong scientific basis (Hirsch 2011) Basins urbanization lead to change in FF distributions Groundwater depletion affecting baseflow and low flow regime And these are not related to climate change Nonstationarity or changing normal

29 29 Can be reflected by various changes such as in: Regional air temperature Water demand as a function of temperature Patterns of rain and snow Timing of snowmelt Frequency and magnitude of hydrologic extreme events Land use/cover How does NYC address this issue ? Nonstationarity

30 30 Simulates water supply by routing water between reservoirs, while accounting for various rules and competitive goals Supports water supply operations and planning needs High flexibility, improved inflow forecast NYC Operations Support Tool

31 31 The events of Fall 2011 were unprecedented in this region due to a combination of: the magnitude of precipitation in each event the proximity in space and time of the two events antecedent and subsequent precipitation As a result, Fall 2011 had the highest 60-day precipitation total on record in this region Conclusions

32 32 The frequencies of extreme warm season hydrologic events have risen to their highest values on record during the last two decades While this study does not address potential for these patterns to continue into the future, these results are consistent with other recent empirical studies, and with 21 st century projections based on climate models Conclusions (contd)

33 33 Nonstationarity is a concern in hydrology and needs to be addressed It need to be accounted for in water resources planning and management The NYC OST is a good example for a flexible management tool to face todays challenges Conclusions (contd)

34 34 Deep gorge created in Frost Valley (Ulster County Route 47) when floods after Hurricane Irene blew out a culvert below the road in Oliverea, NY.

35 35 Cold seasonWarm season 30-day Precipitation 30-day Streamflow Number of 95%tile values per year: all stations

36 36 Cold seasonWarm season 60-day Precipitation 60-day Streamflow Number of 95%tile values per year: all stations

37 37 Ashokan reservoir during a turbidity event. Turbid water moving from West to East basins (2006) Extreme Events Can Affect Water Quality


Download ppt "Hydrological Impact of Hurricane Irene and Tropical Storm Lee in Historical Context: Is the Frequency and Magnitude of Extreme Hydrological Events Changing."

Similar presentations


Ads by Google