Looking beyond 2010… Offsetting Nutrient Loads in the Face of Urban Growth

1. Looking beyond 2010… Offsetting Nutrient Loads in the Face of Urban Growth Reevaluation Workshop September 21, 2005 Ted Graham, Chair Land, Growth, and Stewardship Subcommittee

2. Major Points 1. Urban development is the fastest growing source of nutrients to the Bay. 2. Urban development, including wastewater, contributes more nutrients to the Bay than agriculture. 3. The C2K goal to achieve and maintain water quality can only be met if new urban loads are offset. 4. Projections of urban development and loads beyond 2010 are needed to estimate the scale of required offsets. 5. Analysis is needed to determine what constitutes an effective offset program.

3. Proposal • Forecast future land use • Project land use to 2030 • Better capture population affects on land conversion. • Improve ability to forecast different land conversion scenarios. • LGSS takes the lead in partnership with NSC.

4. Housing Trends 1960 – 1990 (census block groups) Total Housing Units 1960 Total Housing Units 1970 Total Housing Units 1980 Total Housing Units 1990 Historical Block Group Analysis courtesy of D. Theobald, 2001

5. Development “Hot Spots” (1990 – 2000)

6. Nitrogen Loads to the Chesapeake Bay Watershed (Total Loads – Overall Program Focus and Overall Growth) Agriculture Urban/Suburban

7. Nitrogen Loads to the Chesapeake Bay Watershed (Total Loads – Overall Program Focus Excluding Overall Growth) Total loads to the Chesapeake Bay in million pounds per year answer questions concerning overall program focus. When “urban/suburban” total loads consider only the stormwater runoff from the land area, the question of “urban/suburban” loads versus agricultural loads treats population as a given and speaks to land conversion. In this case for nitrogen, total agricultural loads exceed urban/suburban runoff – looking at the scale of the Chesapeake Bay watershed as a whole.

8. Forecasting Future Land Use • Between 1990 and 2000: • population increased 8% • impervious surfaces increased 41% • Because: • Smaller family size • Bigger houses • Larger commercial and retail parking lots “If recent trends continue, the area of developed land in the (Bay) watershed will increase by more than 60% by 2030” ~ “Chesapeake Futures: Choices for the 21st Century”, STAC 2003.

9. Development Pressure in the Chesapeake Bay Watershed (1990 – 2000)

10. Nitrogen Loads to the Chesapeake Bay Watershed (Total Loads – Overall Program Focus Excluding Overall Growth) Total loads to the Chesapeake Bay in million pounds per year answer questions concerning overall program focus. When “urban/suburban” total loads consider only the stormwater runoff from the land area, the question of “urban/suburban” loads versus agricultural loads treats population as a given and speaks to land conversion. In this case for nitrogen, total agricultural loads exceed urban/suburban runoff – looking at the scale of the Chesapeake Bay watershed as a whole.

12. Urban Development May Impact Restoration Progress: Flow-Adjusted Trend in Total Nitrogen DRAFT

13. Nitrogen Loads to the Chesapeake Bay Watershed (Total Loads – Overall Program Focus Excluding Overall Growth) Total loads to the Chesapeake Bay in million pounds per year answer questions concerning overall program focus. When “urban/suburban” total loads consider only the stormwater runoff from the land area, the question of “urban/suburban” loads versus agricultural loads treats population as a given and speaks to land conversion. In this case for nitrogen, total agricultural loads exceed urban/suburban runoff – looking at the scale of the Chesapeake Bay watershed as a whole.

14. Nitrogen Loads to the Chesapeake Bay Watershed (Total Loads – Overall Program Focus and Overall Growth)

15. Forecasting to 2030 • 20 Years is an accepted planning horizon for: • Capital investments (STP) • Comprehensive Planning • Population projections • We can capture enough of a change that we can plan for the impact (offsets, trading). • Ongoing Growth modeling work is targeting 2030.

16. LGSS as Lead . . . • Most of the change is related to where and how the watershed is growing. • LGSS is working on 2 types of growth models that STAC will peer review this winter. • Best suited to understanding the factors that impact decisions on growth patterns.

17. SLEUTH model calibration mapped modeled The greater Baltimore – Washington DC metropolitan area, circa 2000 Jantz C. A., Goetz S. J. & Shelley M. A. (2003) Using the SLEUTH urban growth model to simulate the land use impacts of policy scenarios in the Baltimore-Washington metropolitan region.Environment and Planning (B) 31(2): 251-271.

18. . . . In Partnership with NSC . . . • Tributary Strategy Workgroup has vital experience needed to complete a new land use. • NSC has experience with Agricultural projections and the Ag Census . . . Modeling . . . • Coordination with Phase V watershed model.

19. Recommendations 1. LGSS be tasked with preparing 2030 development projections. 2. LGSS (Land Assessment Team) be tasked with revising the growth allocation models to drive the Phase V Watershed Model. 3. LGSS and NSC be tasked with estimating 2030 nutrient projections by major watershed. 4. LGSS and NSC, in consultation with LGAC, be tasked with defining the framework of an urban development offset program. TIMING: • By December 2005, present a work plan to the IC. • By December 2006, present an interim report to the IC. • By June 2007, present a final report to the IC, including any recommendations for follow on work.

20. Proposal for Discussion • Forecast future land use? • Project land use to 2030? • Better capture population affects on land conversion? • Improve ability to forecast different land conversion scenarios? • LGSS takes the lead in partnership with NSC? • Proposed time-line match partnership needs?

21. Activity Completion Date Proposed Timeline STAC Peer review of Urban Growth Models February 2006 Development of alternative future scenarios; Development of agricultural forecasts; Development of a nutrient offset strategy June 2006 Coupling agricultural and urban forecasts; Simulation of alternative future scenarios; September 2006 Phase V model runs using future scenarios Winter 2006 Pilot implementation of nutrient offset strategy June 2007