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Comprehensive Watershed Master Plan
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Little Salt Creek Watershed Master Plan
Little Salt Creek Watershed Master Plan
June 2009
Documents in PDF format.
Download Complete Report
(28 M Zip PDF)
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Cover and Table of Contents
(443 M)
Executive Summary
(615 K)
Section 1 – Introduction and Purpose
(388 K)
1.1 Introduction
1.2 Goals and Objectives
1.2.1 Goals and Criteria
1.2.2 Watershed Inventory
1.2.3 Hydrology and Hydraulics
1.2.4 Water Quality
1.2.5 Geomorphic
1.2.6 Soil Assessment
1.2.7 Structures
1.2.8 Public Involvement & Facilitation
1.2.9 Capital Improvement Projects
1.2.10 Potential Guidelines/Ordinances
1.2.11 Technical Advisory Committee (TAC)
1.3 Public Participation Process
1.3.1 Open House Events
1.3.2 Citizen Advisory Committee
1.3.3 Website and Newsletter
1.4 Technical Advisory Committee
Section 2 – Data Collection and Development
(424 K)
2.1 Watershed Inventory
2.2 Hydraulic Structure Field Survey
2.3 Base Mapping/Triangular Irregular Network
2.4 Geomorphic Investigation
2.4.1 Geomorphic Background Investigation
2.4.2 Geomorphic Field Investigation
2.4.3 Supplemental Geomorphic Aerial Photo Analysis
2.5 Soil Assessment
2.5.1 Methodology
2.5.2 Dispersive Soils
2.5.3 Saline Seeps
2.5.4 Summary and Recommendations
2.6 Existing Projects and Conservation Easements
Section 3 – Hydrologic Model Development
(1.44 M)
3.1 Introduction
3.1.1 Basin Description
3.2 Methodology
3.2.1 Incorporation of Previous Little Salt Creek Model
3.2.2 Basin Delineation
3.2.3 Rainfall
3.2.4 Runoff Volume Calculation
3.2.5 Runoff Hydrographs (Lag Time)
3.2.6 Routing
3.3 Model Verification
3.3.1 Statistical Analysis of Stream Gauge Data
3.4 Sensitivity Analysis
3.5 Model Calibration
3.5.1 Historical Storm Event Calibration
3.6 Modeling Results
3.7 Future Land Use
3.7.1 Calculation of Existing and Future Curve Numbers
3.7.2 Calculation of Changes to Initial Storage
3.7.3 Guidelines for Modifying the Hydrologic Model Initial Storage to Account for Future Land Use Changes
3.7.4 Modifying the Hydrologic Model Lag Time to Account for Future Land Use Changes
Section 4 – Hydraulic Model Development
(1.08 M)
4.1 Introduction
4.2 HEC-RAS Model Development
4.2.1 Stream Network, Cross Sections, and Reach Lengths
4.2.2 Manning’s n-Values
4.2.3 Roadway Crossings
4.2.4 Expansion and Contraction Coefficients
4.2.5 Ineffective Flow Areas
4.2.6 Boundary Conditions
4.3 Special Modeling Cases
4.3.1 Split Flow Locations
4.3.2 Multiple Structure Analysis
4.3.3 Roadway Skew Analysis
4.4 Model Calibration
4.5 Floodway Determination
Section 5 – Floodplain Management Tools
(3.23 M)
5.1 Introduction
5.1.1 Floodplain Delineation Process
5.1.2 Study Floodplain and Floodway Maps
Section 6 – Water Quality and Bio-Assessment
(616 K)
6.1 Water Quality
6.1.1 Water Quality Discussion
6.2 Stream Bio-Assessment
6.2.1 Stream Bio-Assessment Results
6.3 Water Quality & Bio-Assessment Summary
6.4 Water Quality Future Land Use Hydrology
6.4.1 Hydrology Modeling of Future Land Use
6.4.2 Low Flow Analysis
Section 7 – Drainage Criteria and Ordinance Review
(93 K)
7.1 Introduction
7.2 Storm Water BMPs
7.2.1 Integrated Detention Facility
7.2.2 Alternative Site Design
7.3 Dispersive Soils
7.4 Conservation Culvert or Crossing
7.5 Adopt Revised Floodprone Area as Best Available Information
Section 8 – Geomorphic Evaluation
(899 K)
8.1 Fundamentals of Fluvial Geomorphology
8.1.1 Major Models
8.1.2 Temporal and Spatial Implications
8.1.3 Sediment Transport
8.2 Little Salt Creek Evaluation
8.2.1 Channel Geometry
8.2.2 Boundary Material
8.2.3 Hydraulics
8.2.4 Sediment Transport Competency
8.3 Physical Stability of the Watershed
8.3.1 Existing Channel Process
8.4 Methods of Management
8.4.1 Watershed-Scale Stability
8.4.2 Local Stability
8.4.3 Conclusions
Section 9 – Capital Improvement Projects
(1.71 M)
9.1 Introduction
9.2 Capital Improvement Projects
9.2.1 Problem Identification
9.2.2 Evaluation Approach
9.2.3 Stream Stability Projects
9.3 Other Improvement Recommendations
9.3.1 Problem Identification
9.3.2 Project Evaluation Approach
9.4 Prioritization
Section 10 – Implementation
(42 K)
10.1 Introduction
10.2 Implementation of Capital Improvements
10.3 Policy and Ordinances and Resolutions
10.4 Education Program
10.5 Project Funding
10.6 Coordination Efforts
10.7 Additional Studies
10.7.1 Additional Studies Summary
10.7.2 Phase II Scoping
Section 11 – Glossary of Terms and References
(55 K)
11.1 Glossary of Terms
11.2 References
Appendices
Appendix A - Digital Deliverables
Appendix B - Public Participation Materials (Summary Documents, Attendance Lists, Minutes, Watershed News)
(4.58 M)
Appendix C - Hydrologic Model Input Data and Results
(647 K)
Appendix D - Hydraulic Model Input Data and Res
(134 K)
Appendix E - Aerial Photograph Interpretation
(725 K)
Appendix F - Hydraulic Structure Survey and Design Data
(1.02 M)
Appendix G - Geomorphic Data Summary By Reach
(83 K)
Appendix H - Soil Assessment Data
(490 K)
Appendix I - Watershed Inventory Data Table
(16 K)
Appendix J - Capital Improvement Project Prioritization Ranking Worksheets
(163 K)
Appendix K - Capital Improvement Project Cost Worksheets
(75 K)
Appendix L - Other Improvement Recommendations
(580 K)
Appendix M - Stream Profiles
(5.46 M)
Appendix N - Hydraulic Structure Performance Data
(36 K)
Appendix O - Water Quality and Bio-Assessment Reports
(1.54 M)
Appendix P - Groundwater Seep Survey Data
(1.04 M)
Figures
ES-1 Comprehensive Watershed Master Plan
ES-2 Little Salt Creek Watershed Map
ES-3 Little Salt Creek Floodplain Map Updates
ES-4 Little Salt Creek Capital Improvement Project Location Map
1-1 Comprehensive Watershed Master Plan
1-2 Little Salt Creek Watershed Map
1-3 Project Organization Chart
1-4 Information stations at the public meetings
1-5 April 2008 Issue
1-6 Website information
2-1 North 1st Street Bridge
2-2 Concrete box culvert under Waverly Road
2-3 Little Salt Creek Hydraulic Structures Survey Map
2-4 Little Salt Creek Soil Boring Location Map
2-5 Little Salt Creek Dispersive Clays Location Map
2-6 Little Salt Creek Existing Project Locations Map
3-1 Little Salt Creek Watershed Map
3-2 Little Salt Creek Study Area Comparison
3-3 Little Salt Creek Subbasin Delineation Map
3-4 Little Salt Creek Existing Land Use
3-5 Little Salt Creek Hydrologic Soil Groups
3-6 Graphical Depiction of the Peak Flood Flow Frequency Analysis
3-7 Graphical Depiction of the Volume-Duration-Frequency Analysis
3-8 Little Salt Creek USGS Gauge Location
3-9 HEC-HMS calibration results compared versus the USGS gauge data
3-10 HEC-HMS calibration results (shifted) compared versus the USGS gauge data
3-11 Little Salt Creek HMS Results Locations Map
3-12 Little Salt Creek Future Land Use
4-1 Little Salt Creek Hydraulically Modeled Streams
4-2 thru 4-5 Little Salt Creek Split Flow Locations Map
4-6 thru 4-9 Little Salt Creek Multiple Structures Location Map
4-10 Comparison of HEC-RAS Model Output with the Rating Curve Provided by the USGS
5-1 thru 5-13 Little Salt Creek Floodplain Map Updates
6-1 Little Salt Creek Water Quality and Bio-Assessment Sampling Locations Map
6-2 Total Dissolved Solids Results
6-3 Total Suspended Solids Results
6-4 Rock Creek Road sample site facing upstream
6-5 Arbor sample site facing upstream
6-6 Weibull analysis of Little Salt Creek average daily flows at N 27th St and Arbor Rd
6-7 Little Salt Creek location of Flow Results
6-8 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 1
6-9 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 1(first 6 hours of runoff)
6-10 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 2
6-11 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 2 (first 6 hours of runoff)
6-12 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 3
6-13 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 4
6-14 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 5
6-15 0.5" runoff event resultant hydrographs of existing and future conditions scenarios at Location 6
7-1 Conservation culvert example
8-1 Lane's Stable Channel Balance
8-2 Dynamic equilibrium channel on the mainstem of Little Salt Creek
8-3 Incised V-shaped channel on Tributary 220
8-4 Deposition on Little Salt Creek Mainstem at W. Davey Road culvert
8-5 Channel Evolution Model (from Simon, 2001)
8-6 Meander Formation and Migration
8-7 Meander geometry
8-8 Little Salt Creek Hydraulic Gradient Map
8-9 Erodibility vs. 2-yr Hydraulic Gradient Graph
8-10 Stages of a river system (adapted from Rienick and Singh, 1980)
8-11 General channel profile of a watershed
8-12 Effect of dam resetting the stream formation sequence
8-13 Effect of stream crossings resetting the stream formation sequences
8-14 Hydrograph and Sedigraph
8-15 Little Salt Creek Observed Groundwater Seeps Map
8-16 Little Salt Creek Groundwater Seep Survey Locations
8-17 Little Salt Creek Existing Channel Process
9-1 Projected incision of Little Salt Creek between Raymond Rd and Bluff Rd
9-2 Little Salt Creek Capital Improvement Project Location Map
9-3 Rock Grade Control Structure Detail
9-4 Sheet Pile Grade Control Structure Detail
9-5 Stilling Basin Structure Detail
9-6 Waverly Road Bridge over Main Stem
9-7 Project 1 Proposed Improvements
9-8 North 14th Street Bridge over Main Stem
9-9 Project 2 Proposed Improvements
9-10 Mill Road Bridge over Main Stem
9-11 Project 3 Proposed Improvements
9-12 North 1st Street Bridge over Main Stem
9-13 Project 4 Proposed Improvements
9-14 W Raymond Road Bridge over Main Stem
9-15 Project 5 Proposed Improvements
9-16 NW 12th Street Bridge over Main Stem
9-17 Project 6 Proposed Improvements
9-18 W Branched Oak Road Bridge over Main Stem
9-19 Project 7 Proposed Improvements
9-20 North 19th Street Bridge over Main Stem
9-21 Project 8 Proposed Improvements
9-22 W Rock Creek Road Bridge over Main Stem
9-23 Project 9 Proposed Improvements
9-24 W Agnew Road Bridge over Main Stem
9-25 Project 10 Proposed Improvements
9-26 North 40th Street Culvert on Tributary 10
9-27 Project 11 Proposed Improvements
9-28 North 40th Street Culvert on Tributary 110
9-29 Project 12 Proposed Improvements
9-30 North 40th Street Culvert on Tributary 220
9-31 Project 13 Proposed Improvements
9-32 Waverly Road Culvert on Tributary 35
9-33 Project 14 Proposed Improvements
9-34 North 1st Street Culvert on Tributary 30
9-35 Project 15 Proposed Improvements
9-36 Oak Road Culvert on Tributary 45
9-37 Project 16 Proposed Improvements
9-38 W Davey Road Culvert on Tributary 1260
9-39 Project 17 Proposed Improvements
9-40 Davey Road Culvert on Tributary 260
9-41 Project 18 Proposed Improvements
9-42 Little Salt Creek Hydraulic Structures Survey Map
Tables
ES.1 Capital Improvement Project Summary Results
2.1 Geomorphic Field Data Themes
3.1 Rainfall depths corresponding to each return period (note 500-yr depth is interpolated)
3.2 Lookup table used to define the curve number for each land use-soil group combination
3.3 Constant loss rates as defined by Skaggs and Khaleel (1982)
3.4 Results of the peak flood flow frequency analysis
3.5 Results of the volume-duration-frequency analysis
3.6 Comparison of peak flows resulting from modifications to each basin's initial loss parameter
3.7 Comparison of cumulative volumes resulting from modifications to each basin's initial loss parameter
3.8 HEC-HMS model results compared to the flood flow frequency analysis
3.9 HEC-HMS model results compared to the volume-duration-frequency analysis
3.10 HEC-HMS model resultant peak flows for the 2-, 5-, and 10-yr return periods
3.11 HEC-HMS model resultant peak flows for the 50-, 100-, and 500-yr return periods
3.12 HEC-HMS model resultant cumulative volumes for the 2-, 5-, and 10-yr return periods
3.13 HEC-HMS model resultant cumulative volumes for the 50-, 100-, and 500-yr return periods
3.14 Lookup table used to define the curve number for each land use-soil group combination
3.15 Breakdown of future land uses applied to agricultural lands within Tier 2
3.16 Calculated increases in imperviousness for the Tier 1 future land use scenario
3.17 Calculated increases in imperviousness for the Tier 2 future land use scenario
3.18 Guideline for modifying subbasin initial storage depth based on change in curve number
3.19 Look up table for the lag time multiplying factor due to changes in curve number (future CNs ranging from 62-80)
3.20 Look up table for the lag time multiplying factor due to changes in curve number (future CNs ranging from 81-98)
4.1 HEC-RAS Model Data Sets
4.2 Range of Manning's n-values utilized
4.3 Contraction and expansion coefficients utilized
4.4 Frequencies for coincidental occurrence based upon the ratio of watershed sizes
4.5 Assigned boundary condition stages for the Little Salt Creek
4.6 Locations and frequencies of the split flows
4.7 Locations and frequencies of multiple opening analysis
4.8 HEC-RAS model output at the gauge location
5.1 Little Salt Creek Confluence Level Pool Elevations (NAVD88)
6.1 Nebraska ICI Rating by Sample Site
6.2 Comparison of peak flows under existing and future conditions for the 0.5" runoff event
6.3 Comparison of total volumes under existing and future conditions for the 0.5" runoff event
6.4 Comparison of volumes within the first six hours of runoff under existing and future conditions for the 0.5" runoff event
8.1 Hydraulic Slope and Fluvial Geomorphic Process
9.1 Bridge and Culvert Topping
9.2 Capital Improvement Project Summary Results
Related
Lower Little Salt Creek Watershed - Interim Stormwater Hydrology and Hydraulics Report
(47.2 M Zip)
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