Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Density Paul Radomski DNR Research Scientist Welcome. This is a short presentation that was given to advisory committees of the Shoreland Rules Update Project in the fall of 2008. 1 Objectives • Consequences of human density on water quality • Introduction to potential standards The objectives of this short presentation was to outline the consequences of density on water quality and then introduce various options for consideration. 2 Data from the PCA on impervious surface coverage for Detroit Lakes, MN. 3 Lu et al. 2006, Elvidge et al. 2007, Chabeave et al. 2004 As density increases, the amount and percent of impervious surface increases. Much of the increase in impervious surface is attributable to the increase in roads as density increases. 4 Schueler 2003 An increase density has implications on the quality of the aquatic biota. 5 Cumulative Impacts of Impervious Cover Protected 0 20 Impacted 40 Degraded 60 80 100 Watershed Impervious Cover Schueler 2003, Wang et al. 2001, adapted from NEMO The amount of impervious cover is a key indicator of the quality of the water flowing into our lakes. Research consistently shows that as the amount of impervious surface increases in the watershed, the health of the lake inlets decreases. Streams draining watersheds with more than 12% imperviousness have shown to be consistently in poor condition, indexed by poor fish communities (Wang et al. 2001). Average % of Impervious Cover by Land Use: 2-acre Residence: 12 1-acre Residence: 20 0.5-acre Residence: 25 0.33-acre Residence: 30 0.25-acre Residence: 38 0.125-acre Residence: 65 Industrial: 75 Commercial: 85 Shopping Center: 95 Studies have shown that 55-75% of impervious surfaces are for vehicles, 35% for human habitat. As impervious cover increases, runoff increases linearly. 6 As watersheds become developed, management of stormwater becomes critical. Runoff from homes, lots, driveways, and roads picks up pollutants and moves downhill and downstream. 7 Courtesy UW – Green Bay Failure to address added runoff results in poor water quality, increases in algal bloom, and greater frequency of poor water conditions. 8 Phosphorus Pollution increases with % Impervious Cover Scheuler and Caraco 2001 The predicted benefits in this example watershed show that stormwater treatment practices (STP) with better site design (BSD; or low-impact development) can reduce phosphorus loading and running off into lakes. The practices include infiltration basins, bioretention systems, and low impact designs such as rain gardens. 9 Typical residential development changes the hydrology of streams. The loss of rainwater infiltration with development leads to less groundwater recharge, which means lower base river flows. Higher runoff with development leads to high peak flows, which blows out stream channels (next slide). 10 Stream Channel Blowout CWP As impervious surface coverage increase, the probability of destroying the stream channel increases. 11 Impact of Conventional Development on Habitat Excellent Stream Habitat Original Bank Some Urbanization A comparison of two streams, one in a watershed with little runoff (left) and one in a watershed with poor stormwater management. 12 Fish Species Richness in Streams Wang et al. 2001 Impacts of Urbanization on Stream Habitat and Fish Across Multiple Spatial Scales LIZHU WANG, JOHN LYONS, PAUL KANEHL, ROGER BANNERMAN ABSTRACT / We analyzed the relation of the amount and spatial pattern of land cover with stream fish communities, in-stream habitat, and baseflow in 47 small southeastern Wisconsin, USA, watersheds encompassing a gradient of predominantly agricultural to predominantly urban land uses. The amount of connected impervious surface in the watershed was the best measure of urbanization for predicting fish density, species richness, diversity, and index of biotic integrity (IBI) score; bank erosion; and base flow. However, connected imperviousness was not significantly correlated with overall habitat quality for fish. Nonlinear models were developed using quantile regression to predict the maximum possible number of fish species, IBI score, and base flow for a given level of imperviousness. At watershed connected imperviousness levels less than about 8%, all three variables could have high values, whereas at connected imperviousness levels greater than 12% their values were inevitably low. Connected imperviousness levels between 8 and 12% represented a threshold region where minor changes in urbanization could result in major changes in stream condition. In a spatial analysis, connected imperviousness within a 50-m buffer along the stream or within a 1.6-km radius upstream of the sampling site had more influence on stream fish and base flow than did comparable amounts of imperviousness further away. Our results suggest that urban development that minimizes amount of connected impervious surface and establishes undeveloped buffer areas along streams should have less impact than conventional types of development. 13 Mallin et al. 2000 Ecological Applications, 10(4), 2000, pp. 1047–1056 EFFECT OF HUMAN DEVELOPMENT ON BACTERIOLOGICAL WATER QUALITY IN COASTAL WATERSHEDS MICHAEL A. MALLIN, KATHLEEN E. WILLIAMS, E. CARTIER ESHAM, AND R. PATRICK LOWE 14 Pollution from Septic Systems • Excess nutrients – nitrogen and phosphorus p t ic d se re r a a nd S ta ste m s e m o v e r sy o t T ed ns N O n g i d e s th o g e n ts p a u t r ie n Septic systems, while generally good a slowing down the migration of phosphorus to the lake, do create environmental problems. 15 Cabana and Rasmussen 1996 At low population densities, nitrogen enrichment has been observed in aquatic systems. Proc. Natl . Acad. Sci . USA Vol. 93, pp. 10844 –10847, October 1996 Ecology Comparison of aquatic food chains using nitrogen isotopes GILBERT CABANA AND JOSEPH B. RASMUSSEN 16 Mean % Emergent and Floating-leaf Vegetation Coverage 14.0 12.47 Undeveloped Shore Developed Shore 12.0 10.0 8.55 8.30 8.0 6.0 4.61 4.0 2.82 2.50 2.0 0.0 lightly developed lake moderately developed lake highly developed lake Relative Total Lake Development Radomski and Goeman 2001 Vegetative coverage was estimated in 12 randomly selected 935-m 2 digitized photograph plots for both developed and undeveloped shorelines of 44 lakes representing a gradient of development. Vegetative cover in littoral areas adjacent to developed shores was less abundant than along undeveloped shorelines. On average, there was a 66% reduction in vegetation coverage with development. The above graph shows the vegetative coverage by relative total lake development. 17 25 20 Natural Environment Plant cover lost (%) 15 10 5 0 25 20 Recreational Development 15 10 5 0 25 20 General Development 15 10 5 0 1939 1955 1960 1969 1978 1989 1996 2003 Time period Radomski 2006 Mixed-effects models indicated floating-leaf and emergent vegetative cover (% of lake surface, transformed) was significantly affected (P < 0.1) by development (docks variable). Increases in shoreline development, indexed by dock sites per km, reduced plant cover. The preferred model, judged by the lowest Akaike’s information criteria (AIC) score, to estimate vegetative cover loss was a linear mixed-effects model with time, shoreland development class, timing of photograph within the year, and the between time and shoreland development class interaction as fixed effects and dock sites per kilometer (transformed) as a linear effect. Since two-way interactions between shoreland development class and time were observed, mean comparisons were conducted according to the twoway interaction. This linear mixed-effects model estimated the mean floating-leaf and emergent vegetation cover loss in 2003 from development was 6% for natural environment class lakes, 14% for recreational development, and 17% for general development class lakes. The weighted average vegetation cover loss in 2003, weighted by surface area in each shoreland development class, was 15% for the five county northcentral Minnesota area. 18 Radomski and Goeman 2001 Even though fish surveys have considerable measurement uncertainty and the correlations were low, this comparative analysis suggests that declines in emergent and floating-leaf vegetation due to development may result in lower fish production. (And analysis by other investigators support this). North American Journal of Fisheries Management 21:46–61, 2001Consequences Of Human Lakeshore Development on Emergent and Floating-Leaf Vegetation Abundance PAUL RADOMSKI AND TIMOTHY J. GOEMAN Minnesota Department of Natural Resources, Division of Fisheries, 1601 Minnesota Drive, Brainerd, Minnesota 56401, USA Abstract Vegetation abundance along undeveloped and developed shorelines of Minnesota lakes was compared to test the hypothesis that development has not altered the abundance of emergent and floating-leaf vegetation. Aerial photographs of clear-water lakes dominated by centrarchids and walleyes Stizostedion vitreum were analyzed for vegetation. Vegetative coverage was estimated in 12 randomly selected 935-m 2 digitized photograph plots for both developed and undeveloped shorelines of 44 lakes representing a gradient of development. Vegetative cover in littoral areas adjacent to developed shores was less abundant than along undeveloped shorelines. On average, there was a 66% reduction in vegetation coverage with development. The estimated loss of emergent and floating-leaf coverage from human development for all Minnesota’s clearwater centrarchid–walleye lakes was 20–28%. Significant correlations were detected between occurrence of emergent and floating-leaf plant species and relative biomass and mean size of northern pike Esox lucius, bluegill Lepomis macrochirus, and pumpkinseed Lepomis gibbosus (Spearman’s rank correlation, P < 0.05). Current shoreline regulatory policies and landowner education programs may need to be changed to address the cumulative impacts to North American lakes. 19 Build-out Predictions Itasca County Lake Sensitivity Project, Rian Reed, Minnesota DNR Scientific models used to estimate water clarity and phosphorus levels for our lakes can be used to predict the consequences of development build-out with our existing shoreland rules. This prediction for a lake in Itasca County shows that as more development occurs around the lake, water clarity declines. 20 21 22 Asplund 1996 Average change from weekday to weekend for shallow and deep lakes studied in Wisconsin by Tim Asplund. Boat density increased on weekends, and water clarity decreased by about 16 inches in the shallow lakes and about 8 inches in the near-shore areas of all lakes. 23 Watercraft and Waterfowl • Loss of feeding time • Energy loss • Reduced breeding success • Reduced survival of chicks Korschgen and Dahlgren 1992, Cywinski 2004 1. Kahl (1991) found that disturbance in a Wisconsin lake resulted in about a 50% reduction in feeding time for canvasbacks. 2. Knapton (2000) found that disturbance lead canvasbacks, redheads, and scaup to feed in less productive areas. 3. Belanger and Bedard (1990) found for snow geese that disturbance caused a 5.3% increase in hourly energy expenditure. 4. Disturbance can cause female nesting ducks to take flight, leaving eggs exposed. And chicks are more prone to predation after disturbance. 5. Korschgen and Dahlgren (1992) reviewed over 200 investigations, and this review revealed that disturbance from development displaced waterfowl from feeding grounds, increased energetic costs associated with flight, and likely lowered productivity of nesting or brooding waterfowl. 24