Fictional Demonstration Decision Brief — Cedar Hollow Watershed Council…

FICTIONAL DEMONSTRATION BRIEF — invented watershed-council scenario Scope and assumptions. The fictional council must select exactly two interventions: capital cost ≤ EUR 1,200,000, restored habitat ≥40 ha, and maximum readiness time ≤18 months. Sediment reductions are mature annual values, additive, and have no synergies or interactions. These are scenario inputs, not real-world measurements or predictions. Baseline pair evaluation (cost; habitat; maximum readiness; reduction): • Riparian buffers + Wetland restoration: EUR 420,000+620,000=1,040,000; 18+24=42 ha; max(9,18)=18 months; 54+92=146 t/year. FEASIBLE. • Riparian buffers + Slope replanting: EUR 770,000; 48 ha; 12 months; 90 t/year. FEASIBLE. • Riparian buffers + Retention basin: EUR 960,000; 21 ha; 9 months; 164 t/year. INFEASIBLE: habitat is 21<40 ha. • Wetland restoration + Slope replanting: EUR 970,000; 54 ha; 18 months; 128 t/year. FEASIBLE. • Wetland restoration + Retention basin: EUR 1,160,000; 27 ha; 18 months; 202 t/year. INFEASIBLE: habitat is 27<40 ha. • Slope replanting + Retention basin: EUR 890,000; 33 ha; 12 months; 146 t/year. INFEASIBLE: habitat is 33<40 ha. Recommendation. Select Riparian buffers + Wetland restoration: 146 t/year, the greatest reduction among feasible pairs. It restores 42 ha and meets the 18-month limit, but costs EUR 1.04m and has slower readiness than the riparian+slope alternative. The basin has the highest raw reduction in combinations (202 t/year with wetlands) but fails the habitat requirement; slope offers more habitat at lower cost but less reduction. Stress cases. (1) If wetland performance falls 30%, its reduction is 92×0.70=64.4 t/year, with all other inputs unchanged. Pair reductions become: riparian+wetland 54+64.4=118.4; riparian+slope 90; riparian+basin 164; wetland+slope 64.4+36=100.4; wetland+basin 174.4; slope+basin 146 t/year. Feasibility constraints are unchanged, so riparian+wetland remains the best feasible pair. The exact switching loss L is found by comparing it with riparian+slope: 54+92(1−L)=90, so L=56/92=14/23=60.869565...%. Below 60.869565% loss, riparian+wetland wins; at exactly 14/23 they tie at 90 t/year; above it, riparian+slope wins. Wetland+slope remains 18 t/year below riparian+wetland at every common wetland-performance level. (2) With a EUR 950,000 budget and original reductions, riparian+slope is the only feasible pair: EUR 770,000, 48 ha, 12 months, 90 t/year. Riparian+wetland (EUR 1.04m) and wetland+slope (EUR 970,000) meet habitat/readiness but fail the budget. Riparian+basin (EUR 960,000) also fails the budget and habitat; wetland+basin fails habitat (27 ha) and budget; slope+basin meets budget but fails habitat (33 ha). Implementation, monitoring and gates. Months 0–3: confirm land access, permits, baseline sediment loads, habitat mapping and cost estimates. Gate 1: proceed only if the two selected interventions still satisfy cost, habitat and 18-month constraints. Months 3–9: procure and install buffers; begin wetland design and restoration. Gate 2 at month 9: verify buffer establishment, expenditure and wetland schedule; correct or pause if thresholds are missed. Months 9–18: complete wetland works and operational commissioning. Gate 3 at month 18: accept only after both interventions are operational, habitat targets are documented and monitoring equipment is functioning. Monitor monthly construction cost and schedule; quarterly sediment load, flow, turbidity, buffer survival/coverage, wetland inundation and restored hectares; and annually estimate sediment reduction using the same methods. Trigger redesign or contingency action for material cost overrun, schedule slippage, habitat shortfall, failed vegetation establishment or sediment performance materially below the scenario value. Monitoring can update the decision; it cannot convert these fictional calculations into real-world predictions.