Water and Rivers

Course Grading and Assessment Framework

• Grading distribution weightings:

  • Attendance and participation: $40\%$

  • Exam 1: $20\%$

  • Exam 2: $20\%$

  • Final Exam: $20\%$

• Exemplary calculation scenarios for final course scoring:

  • Scenario A (High performance on assessments):

  • Full attendance credit: $40\%$

  • Assessment average of $85\%$ across all three examinations yields: $17\%$ per exam ($0.85 \times 20\%$)

  • Sum of cumulative scoring components: $40 + 17 + 17 + 17 = 91\%$

  • Scenario B (Moderate performance on assessments):

  • Full attendance credit: $40\%$

  • Assessment average of $75\%$ across all three examinations yields: $15\%$ per exam ($0.75 \times 20\%$)

  • Sum of cumulative scoring components: $40 + 15 + 15 + 15 = 85\%$

Global Hydrologic Distribution and the Water Cycle

• Hydrologic Cycle Fundamental Definition:

  • The hydrologic cycle is defined as the continuous movement of water above, on, and below the surface of the Earth.

  • Terrestrial water can exist in fresh, saline, or mixed (brackish) chemical states.

• Conceptual Framework of Water Budgets (Pools and Fluxes):

  • Pools: Reservoir compartments where water resides for varying residence times (e.g., oceans, ice sheets, groundwater aquifers, atmosphere, lakes, soils, and living biomass).

  • Fluxes: The dynamic processes and pathways by which water transitions between distinct pools (e.g., evaporation, precipitation, discharge, recharge, transpiration, infiltration, and human extraction).

• Primary Dynamic Fluxes of the Hydrologic Cycle:

  • Evaporation: Phase change converting surface liquid water into gaseous atmospheric water vapor driven by solar thermal input.

  • Transpiration: Release of water vapor into the atmosphere through plant stomata.

  • Evapotranspiration: Combined flux of surface water evaporation and biological plant transpiration.

  • Condensation: Phase transition of cooling water vapor in the atmosphere into liquid water droplets or ice crystals, forming clouds.

  • Precipitation: Atmospheric moisture returning to Earth's surface as rain, snow, sleet, or hail.

  • Infiltration: Downward movement of surface water into upper soil layers.

  • Percolation: Deep vertical migration of infiltrated water through unsaturated subsoil toward the saturated groundwater table.

  • Surface Runoff: Overland transport of unabsorbed precipitation across the landscape toward stream channels.

  • Snowmelt Runoff: Meltwater generated from snowpack and mountain glaciers feeding streams and river networks.

  • Groundwater Discharge: Subsurface water draining from saturated aquifers into rivers, lakes, wetlands, or directly into the oceans.

  • Volcanic Gas Emission: Release of juvenile deep-earth water vapor into the atmosphere during volcanic outgassing.

• Planetary Water Inventory by Volume Percentage:

  • Oceans (Saltwater): $97.5\%$

  • Glacial Ice and Ice Sheets: $1.81\%$

  • Groundwater: $0.63\%$

  • Lakes and Streams: $0.016\%$

  • Soil Moisture: $0.005\%$

  • Atmosphere: $0.001\%$

• Global Annual Flux Magnitudes (in Trillions of Gallons):

  • Oceanic evaporation: $112{,}000\,\text{trillion gallons}$

  • Oceanic precipitation: $101{,}000\,\text{trillion gallons}$

  • Terrestrial precipitation: $29{,}700\,\text{trillion gallons}$

  • Terrestrial evapotranspiration: $18{,}700\,\text{trillion gallons}$

  • Streamflow to oceans: $11{,}000\,\text{trillion gallons}$

• Quantitative Terrestrial Water Balance (excluding Antarctica):

  • Global Water Storage Volumes ($\text{Storage} \times 10^3\,\text{km}^3$):

  • Sea / Oceans: $1{,}338{,}000 \times 10^3\,\text{km}^3$

  • Glaciers and Snow: $24{,}064 \times 10^3\,\text{km}^3$

  • Groundwater: $23{,}400 \times 10^3\,\text{km}^3$

  • Permafrost: $300 \times 10^3\,\text{km}^3$

  • Freshwater and Saline Lakes: $175 \times 10^3\,\text{km}^3$

  • Soil Moisture: $17 \times 10^3\,\text{km}^3$

  • Wetlands: $17 \times 10^3\,\text{km}^3$

  • Atmospheric Moisture over Land: $3 \times 10^3\,\text{km}^3$

  • Atmospheric Moisture over Sea: $10 \times 10^3\,\text{km}^3$

  • River Channels: $2 \times 10^3\,\text{km}^3$

  • Biological Water: $1 \times 10^3\,\text{km}^3$

  • Global Annual Volumetric Fluxes ($\text{Flux} \times 10^3\,\text{km}^3/\text{y}$):

  • Evaporation over ocean: $436.5 \times 10^3\,\text{km}^3/\text{y}$

  • Precipitation over ocean: $391 \times 10^3\,\text{km}^3/\text{y}$

  • Net advective water vapor flux transport from ocean to land: $45.5 \times 10^3\,\text{km}^3/\text{y}$

  • Total terrestrial precipitation: $111 \times 10^3\,\text{km}^3/\text{y}$

    • Terrestrial rainfall: $98.5 \times 10^3\,\text{km}^3/\text{y}$

    • Terrestrial snowfall: $12.5 \times 10^3\,\text{km}^3/\text{y}$

  • Total terrestrial evapotranspiration: $65.5 \times 10^3\,\text{km}^3/\text{y}$

  • Total terrestrial runoff returning to oceans: $45.5 \times 10^3\,\text{km}^3/\text{y}$

    • Subsurface runoff: $30.2 \times 10^3\,\text{km}^3/\text{y}$

    • Surface runoff: $15.3 \times 10^3\,\text{km}^3/\text{y}$

  • Land Cover Distribution Areas and Hydroclimatic Fluxes:

  • Grassland: Area = $48.9 \times 10^6\,\text{km}^2$; Precipitation = $31 \times 10^3\,\text{km}^3/\text{y}$; Evapotranspiration = $21 \times 10^3\,\text{km}^3/\text{y}$

  • Forest: Area = $40.1 \times 10^6\,\text{km}^2$; Precipitation = $54 \times 10^3\,\text{km}^3/\text{y}$; Evapotranspiration = $29 \times 10^3\,\text{km}^3/\text{y}$

  • Cropland: Area = $15.6 \times 10^6\,\text{km}^2$; Precipitation = $11.6 \times 10^3\,\text{km}^3/\text{y}$; Evapotranspiration = $7.6 \times 10^3\,\text{km}^3/\text{y}$

  • Lakes: Area = $2.7 \times 10^6\,\text{km}^2$; Precipitation = $2.4 \times 10^3\,\text{km}^3/\text{y}$; Evaporation = $1.3 \times 10^3\,\text{km}^3/\text{y}$

  • Wetlands: Area = $0.2 \times 10^6\,\text{km}^2$; Precipitation = $0.3 \times 10^3\,\text{km}^3/\text{y}$; Evaporation = $0.2 \times 10^3\,\text{km}^3/\text{y}$

  • Other Terrestrial Surfaces: Area = $26.4 \times 10^6\,\text{km}^2$; Precipitation = $11.7 \times 10^3\,\text{km}^3/\text{y}$; Evapotranspiration = $6.4 \times 10^3\,\text{km}^3/\text{y}$

  • Anthropogenic Water Extractions ($\text{Withdrawal} \times 10^3\,\text{km}^3/\text{y}$):

  • Agricultural irrigation: $2.66 \times 10^3\,\text{km}^3/\text{y}$

  • Industrial water use: $0.77 \times 10^3\,\text{km}^3/\text{y}$

  • Domestic water use: $0.38 \times 10^3\,\text{km}^3/\text{y}$

Fluvial Principles: Definitions, Discharge, and Stream Load

• Fundamental Fluvial Terminology:

  • Stream: Any body of flowing water confined within a defined topographic channel, encompassing rivers, creeks, brooks, and runs.

  • Discharge ($Q$): The volume of water passing through a defined cross-sectional plane per unit of time (commonly expressed in cubic meters per second, $\text{m}^3/\text{s}$, or cubic feet per second, $\text{cfs}$).

  • Watershed (Drainage Basin / Catchment): The entire geographic land surface area from which all runoff, tributaries, and groundwater drain into a common outlet or trunk stream.

• Mathematical Determination of Stream Discharge:

  • The continuity equation for open channel flow is defined as:

$Q = A \times V$

• Variables:

  • $Q$ = Stream discharge ($\text{m}^3/\text{s}$)

  • $A$ = Cross-sectional area of channel flow ($\text{m}^2$)

  • $V$ = Mean downstream flow velocity ($\text{m}/\text{s}$)

• Worked Example:

  • Given channel flow cross section $A = 25\,\text{m}^2$

  • Given average stream velocity $V = 5\,\text{m}/\text{s}$

  • Resulting discharge:

$Q = (25\,\text{m}^2) \times (5\,\text{m}/\text{s}) = 125\,\text{m}^3/\text{s}$

- Physical interpretation: Exactly $125\,\text{m}^3$ of water moves past the measured cross-section every $1\,\text{second}$.

• Classification of Stream Load:

  • Bed Load:

  • Coarse, dense clasts (gravel, pebbles, boulders, and coarse sand).

  • Transported along the channel bottom by traction (rolling or sliding) and saltation (hopping and bouncing).

  • Suspended Load:

  • Fine particles (silt and clay) held in suspension within the water column by fluid turbulence.

  • Comprises the majority of physical sediment transported by most large river systems.

  • Dissolved Load:

  • Chemical ions and soluble mineral compounds carried invisibly in aqueous solution (e.g., calcium, bicarbonate, sodium, and chloride derived from chemical weathering).

Watershed Dynamics, Drainage Divides, and Hydrography

• Topographic Organization of Drainage Networks:

  • Tributaries: Smaller branching stream channels that collect runoff and convey water into larger parent trunk rivers.

  • Drainage Divide: A linear topographic ridge or high ground boundary that separates adjacent drainage basins. Precipitation falling on opposite sides of a divide flows toward entirely separate trunk streams.

• Major Continental Divides of North America:

  • Great Divide (Continental Divide): Follows the spine of the Rocky Mountains, segregating waters draining west toward the Pacific Ocean from waters draining east toward the Atlantic Ocean, Gulf of Mexico, or Arctic Ocean.

  • Laurentian Divide (Northern Divide): Separates the drainage basin of Hudson Bay and the Arctic Ocean from the Mississippi River basin and the Great Lakes.

  • Arctic Divide: Defines the hydrographic boundary separating watersheds flowing northward directly into the Arctic Ocean and Beaufort Sea.

  • St. Lawrence Divide: Separates the Great Lakes–St. Lawrence River basin draining into the North Atlantic from the Mississippi River basin draining to the Gulf of Mexico.

  • Eastern Divide: Traverses the Appalachian Mountains, dividing eastward Atlantic seaboard drainage from westward drainage entering the Ohio and Mississippi river basins.

  • Great Basin: An internally draining (endorheic) hydrological catchment with no surface outlet to the ocean, retaining water within terminal closed basins and saline lakes.

  • Hydrographic Triple Divide Points:

  • Snow Dome: Mountain peak situated in Jasper National Park, Alberta, where drainage diverges toward the Pacific Ocean, the Arctic Ocean, and Hudson Bay.

  • Triple Divide Peak: Peak located in Glacier National Park, Montana, functioning as the convergence point where water diverges to the Pacific Ocean, the Atlantic Ocean (via the Gulf of Mexico), and the Arctic Ocean (via Hudson Bay).

• Regional Watershed Systems:

  • Mississippi River Basin: Encompasses the vast central United States, draining into the Gulf of Mexico.

  • Chesapeake Bay Watershed: Covers portions of New York, Pennsylvania, Maryland, Delaware, Virginia, and West Virginia, capturing discharge from major rivers including the Susquehanna River, Juniata River, Potomac River, Shenandoah River, Rappahannock River, and James River.

• Hudson-Raritan Estuary System:

  • Geographic setting: Encompasses metropolitan coastal zones across New York and New Jersey.

  • Key waterways: Hudson River, Passaic River, Hackensack River, Rahway River, Raritan River, and Navesink River.

  • Marine embayments: Newark Bay, Upper Bay, Lower Bay, Jamaica Bay, Raritan Bay, and Sandy Hook Bay.

  • Real-Time Hydrologic Gauging Networks:

• USGS National Water Dashboard monitors streamflow conditions continuously, categorizing stations relative to historical percentiles:

  • $100\text{th}\,\text{percentile}$: Maximum / All-time high for that day of the year.

  • $>90\text{th}\,\text{percentile}$: Much above normal.

  • $76\text{th}-90\text{th}\,\text{percentile}$: Above normal.

  • $25\text{th}-75\text{th}\,\text{percentile}$: Normal flow conditions.

  • $10\text{th}-24\text{th}\,\text{percentile}$: Below normal.

  • $<10\text{th}\,\text{percentile}$: Much below normal.

  • $0\text{th}\,\text{percentile}$: Minimum / All-time low for that day of the year.

River Morphology, Channel Profiles, and Meandering Dynamics

• Longitudinal River Profile and Downstream Trends:

  • Headwaters / Source: Characterized by steep topographic gradient, high gravitational potential energy, narrow V-shaped bedrock valleys, and coarse, angular bed sediment.

  • Downstream Transfer Zone: Valley widens, channel gradient becomes shallower, and sediment clasts undergo rounding, mechanical breakdown, and size sorting.

  • Mouth / Base Level: Characterized by low gradients, low stream velocity, and broad floodplains. When flow enters a standing body of water (lake or sea), forward velocity terminates, causing remaining transported sediment to be dropped.

  • Deltaic Deposition: Deceleration at base level generates dynamic sediment accumulation, forming branching distributaries, alluvial fans, or ocean-entry deltas.

• Cross-Sectional Geometry and Meander Mechanics:

  • Straight Channel Geometry: Features symmetrical cross-sections with maximum flow velocity and channel depth focused along the central line (thalweg).

  • Curved Channel / Meander Bend Geometry: Centrifugal force and helical flow shift the maximum velocity towards the outer boundary:

  • Cut Bank (Outer Bend): Characterized by steep erosional banks, rapid flow velocity, and active lateral undercut erosion.

  • Point Bar (Inner Bend): Characterized by gently sloping depositional margins, reduced flow velocity, and accumulation of bed load sand and gravel.

  • Physical Flume Experiments: Flow visualizations prove that water accelerates along outer cut banks while inner zones experience deposition, driving continuous lateral migration of the channel across the landscape.

• Channel Classification Systems:

  • Channel Count Classification:

  • Single Channel: One continuous flow corridor.

  • Wandering Channel: Semi-stable channel with variable branching count ($1$ to $3$ channels).

  • Braided Channel: Multithread network with high sediment load, unstable bar complexes, and high branching density ($>3$ channels).

  • Anastomosing Channel: Stable, low-gradient multithread channels ($>3$ channels) separated by mature, vegetated, cohesive floodplain islands.

  • Discontinuous Channel: Interrupted channel lines separated by diffuse overland wash or wetlands.

  • Degree of Sinuosity ($\text{Channel Length} / \text{Straight-line Valley Distance}$):

  • Straight: Sinuosity index of $1.0$ to $1.05$

  • Low Sinuosity: Sinuosity index of $1.06$ to $1.3$

  • Sinuous: Sinuosity index of $1.3$ to $3.0$

  • Types of Sinuosity Curves:

  • Regular sinuosity: Consistent, periodic alternating wave patterns.

  • Irregular sinuosity: Asymmetric, non-uniform bends influenced by variable bank resistance or structural controls.

  • Tortuous sinuosity: Extremely exaggerated, convoluted loops.

• Floodplain Evolution and Oxbow Formation:

  • Floodplain: Broad, low-relief strip of valley floor adjacent to a stream channel, constructed of deposited sediment (alluvium) and inundated during overbank flow events.

  • Lateral Migration: Progressive cut bank erosion coupled with point bar deposition sweeps meander loops laterally across the valley floor.

  • Chute / Neck Cutoff: During high-discharge flood stages, water carves a straight, short path across the narrow neck of an exaggerated meander loop.

  • Oxbow Lake: The abandoned former meander loop becomes plugged with sediment at its entrances, leaving an isolated crescent-shaped standing water body.

  • Meander Scrolls: Palimpsest arcuate topographic ridges and swales preserved across the floodplain that map the historical progression of former channel positions.

• Primary Controls on Equilibrium River Morphology:

  • Sediment supply (volume, grain size distribution, and mineral stability).

  • Watershed gradient (topographic slope of the catchment and reach).

  • Water velocity (governed by cross-sectional area, slope, and channel boundary roughness).

  • Channel dimensions (width-to-depth ratios and wetted perimeter).

Anthropogenic River Alteration and Urban Hydrology

• Common Engineering Motivations:

  • Flood mitigation, navigational maintenance, agricultural drainage, industrial extraction, and land reclamation for urban expansion.

• Channelization and Bank Stabilization Techniques:

  • Bank stabilization structures: Rip-rap (loose angular boulder armor), wire gabion baskets, stacked concrete revetment blocks, and vegetated geotextile earth bags.

  • Concrete canalization: Straightening and lining channels with smooth concrete walls and trapezoidal cross-sections to maximize flow velocity and rapidly shed floodwaters.

• Stormwater conveyance: Subsurface road culverts, storm sewer outfall pipes, and street catch basins built to capture urban surface runoff.

• Hydrologic Alterations: Pre-Urban versus Urban Watersheds:

  • Natural / Pre-Urban Baseline Conditions:

  • High precipitation infiltration into deep permeable topsoil.

  • High rates of vegetative transpiration and natural evaporation.

  • Steady subsurface recharge sustaining a high water table and consistent dry-weather stream baseflow.

  • Low, diffuse surface runoff volumes with minimal channel erosion.

  • Urbanized Watershed Conditions:

  • Proliferation of impermeable surfaces (roofs, concrete sidewalks, asphalt roadways).

  • Markedly reduced ground infiltration and depleted water table levels.

  • Reduced natural plant transpiration and altered surface evaporation.

  • Dramatic spike in surface runoff volume and flash flood velocities, causing severe downstream channel erosion.

  • Introduction of contaminated urban nonpoint source runoff (oils, heavy metals, nutrients, and sediments).

  • Creation of "urban karst": Subsurface utility corridors, leaking water mains, broken sewer conduits, and trench backfill that create artificial preferential flow paths.

• River Channel Restoration Approaches:

  • Transitioning heavily engineered, concrete-lined storm flumes into stepped, multi-tier daylighted park corridors that integrate vegetative biofiltration, recreational terraces, and improved aquatic habitat.

• Mareit River Restoration Project (Italy, 2005–2010):

  • Historic condition (2005): Single straightened channel restrained by uniform lateral dikes and rigid concrete drop-weir grade control structures.

  • Restored condition (2010): Removal of grade-control barriers and lateral confinement, allowing the river to re-establish a dynamic, braided multithread channel network with gravel bars, backwaters, and riparian connectivity.

Dam Engineering, Water Supplies, and Ecological Impacts

• Historical and Modern Dam Applications:

  • Historical mill dams: Early industrial run-of-the-river stone dams (e.g., Arnot Mill Dam in Elmira, New York) powering textile and grist mills.

  • Modern multipurpose mega-dams: Hydroelectric generation and massive seasonal storage impoundments (e.g., Hoover Dam on the Colorado River and the Aswan High Dam on the Nile River in Egypt).

  • Agricultural diversions: Gravity-fed furrow irrigation networks using siphon pipes, and extensive levee-bounded flooded fields such as commercial cranberry bogs.

• Mechanical Architecture of Flood Control Dams:

  • Storm Runoff / Inflow: Peak flood hydrographs entering the impoundment from upstream tributaries.

  • Reservoir Storage: Body of water held behind the barrier; includes a dedicated volume termed "Temporary Flood Storage" designed to absorb flood crests.

  • Dam Structure: Concrete gravity, arch, or earthen barrier containing hydraulic pressure.

  • Outlet Works: Bottom gate and conduit assemblies permitting calibrated, low-velocity controlled releases into the downstream channel.

  • Spillway: Reinforced overflow crest designed to safely vent catastrophic surplus water without overtopping or eroding the primary dam structure.

• Regional Water Supply Infrastructure: New York City System:

  • Watershed source areas:

  • Catskill / Delaware Watersheds (situated up to $125\,\text{miles}$ northwest of City Hall across Delaware, Greene, Schoharie, Sullivan, and Ulster Counties).

  • Croton Watershed (situated east of the Hudson River across Westchester and Putnam Counties).

  • Critical reservoir storage bodies:

  • Cannonsville, Pepacton, Neversink, Rondout, Schoharie, Ashokan, West Branch, New Croton, Kensico, Hillview, and Jerome Park reservoirs.

  • Inter-basin hydraulic conveyances:

  • Shandaken Tunnel, West Delaware Tunnel, East Delaware Tunnel, Neversink Tunnel, Delaware Aqueduct, Catskill Aqueduct, New Croton Aqueduct, City Tunnel No. 1, City Tunnel No. 2, and City Tunnel No. 3.

  • Specialized treatment:

  • Catskill/Delaware Ultraviolet (UV) Disinfection Facility and Croton Water Filtration Plant.

• Geomorphological and Water Quality Impacts of Dams:

  • Upstream Impoundment Consequences:

  • Conversion of lotic (flowing) to lentic (still) conditions, reducing dissolved oxygen concentrations and eliminating turbidity currents.

  • Substantial increase in surface water evaporation due to expanded surface area.

  • Thermal stratification, accelerated accumulation of chemical pollutants, and harmful algae blooms.

  • Upstream sediment capture: Bed load and suspended sediment are impounded, burying natural gravel substrates and forming debris jams at the reservoir head.

  • Downstream River Reach Consequences:

  • "Sediment starvation": Clean water discharged downstream possesses excess transport capacity, leading to severe riverbed degradation, channel incision, and armor coarsening.

  • Altered thermal regimes and unnatural flow patterns (hydropeaking) disrupting natural ecological signals.

  • Loss of vital downstream fine nutrient, wood, and sediment supply necessary to maintain floodplains and coastal delta fronts.

• Ecological Disruption of Aquatic Habitat:

  • Fragmentation of River Corridors: Physical barriers block resident and anadromous/catadromous migratory fish (such as salmon) from traveling upstream to historic spawning grounds.

  • Hyporheic Zone Degradation: Hyporheic flow—the critical subsurface interstitial exchange between shallow groundwater and surface river water through bed gravels—is disrupted by altered hydraulic head, bed incision, and silt compaction.

Dam Removal and Ecosystem Renewal

• Decommissioning Drivers for Aging Dam Infrastructure:

  • Structural deterioration, public safety hazards, high maintenance liabilities, sediment reservoir siltation, and federal environmental relicensing requirements.

  • Databases including the National Barrier Inventory, New York State Department of Environmental Conservation (NYS DEC), and the American Rivers Removed Dams database document thousands of legacy dams targeted for removal.

• The Klamath River Renewal Project (Oregon and California):

  • Represents the largest dam removal and salmon restoration initiative in United States history.

  • Focuses on the removal of four major hydroelectric barriers along the Klamath River:

  • J.C. Boyle Dam (Oregon)

  • Copco 1 Dam (California)

  • Copco 2 Dam (California)

  • Iron Gate Dam (California)

  • Project reach extends from Upper Klamath Lake downstream to the Pacific Ocean, reconnecting historic spawning habitat across hundreds of miles for Chinook salmon, Coho salmon, and steelhead trout.

Flood Hydrology, Forecasting, and Inundation Modeling

• Flood Dynamics and Inundation Mapping:

  • Natural overbank flooding occurs when stream discharge exceeds bankfull channel capacity, spilling water across the low-gradient floodplain.

  • Overbank inundation serves crucial environmental functions: recharging alluvial aquifers, depositing nutrient-rich silt, and seeding floodplain vegetation.

• National Water Prediction Service (NOAA / USGS Network):

  • Standard Flood Hazard Stage Classifications:

  • Major Flood: Extensive inundation of structures and primary transit routes; significant evacuation of populations.

  • Moderate Flood: Secondary inundation of structures and roads near streams; localized evacuations.

  • Minor Flood: Minimal property damage; minor public inconvenience or flooding of low-lying roadways immediately along river margins.

  • Action Stage: River surface elevation approaches bankfull capacity; mitigation measures must be initiated.

  • No Flood: Base or standard seasonal flow below alert thresholds.

  • Flood Category Not Defined: Gauges lacking formal established hazard stages.

  • Low Water Threshold: Extremely low flow volumes impacting navigation or municipal intakes.

  • National Gauge Network Operational Status:

  • Observation Metrics: Major Flood = $0$; Moderate Flood = $0$; Minor Flood = $22$; Action = $29$; No Flood = $1376$; Flood Category Not Defined = $625$; Low Water Threshold = $3$; Data Not Current = $112$; Out of Service = $19$.

  • Forecast Metrics: Major Flood = $0$; Moderate Flood = $1$; Minor Flood = $31$; Action = $42$; No Flood = $474$.

• High-Resolution Flood Inundation Mapping (FIM):

  • Advanced NOAA/USGS dynamic mapping providing high-resolution street-level hydraulic inundation coverage across nearly $100\%$ of the contiguous United States.

  • Incorporates topographic LiDAR, structural levee wall data, earthen embankments, and coastal modeling zones to model depth-grid inundation (e.g., Passaic River basin at Wallington and Paterson, New Jersey).