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Using GIS for Managing Flood Plain Ecosystems

Joe Miyamoto, Project Manager EBMUD; Reza Ghezelbash, & Mardi Jackson GIS Consulting & Application Development

Abstract

GIS Solution: GIS use in modeling a flood plain and other ecosystem components as a management tool for East Bay Municipal Water District. Making a modeled ecosystem available and maintainable to natural resource and operations managers allows them to find new solutions to tough issues

Application Methodology:. The flood plain model was developed in order to delineate the flood prone lands along the Lower Mokelumne river below Camanche dam to the intersection of Hwy. 99 (a total of 20.80 miles in length). The flood plain model is then used in conjunction with other layers such as: salmon spawning, wildlife observations, land use, ownership, temperature and soils by managers via ArcView to predict results of and communicate management decisions.

Software: The flood plain modeling application was built in ArcInfo (AWK & AML) for use by managers in ArcView. Additionally, the flood plain model accommodates functional end-user needs such as, plotting and reporting. The purpose of this paper is to demonstrate the use of a flood plain model in managing a riparian ecosystem including: fisheries, wildlife, water quality and land use issues. The encrypted flood plain application has the native interface and feel of an Esri function:

FLOODPLAIN

{map_index} {minimum_mapunit}

{NONE | SOFTCOPY | HARDCOPY} {NOECHO|ECHO}

{USGS | PHOTOGRAMETRY}

Introduction

East Bay Municipal Utility District (EBMUD) provides water to over 1.2 million customers in 20 cities and two counties in the East Bay region of the San Francisco Bay area. A majority of the East Bay's water supply originates from the Mokelumne river which runs from the Sierra crest to the Sacramento-San Joaquin Delta. In addition to providing a reliable water source, EBMUD is responsible for maintaining the aquatic resources of the Lower Mokelumne River (LMR) which reaches from Camanche Dam to the Sacramento San-Joaquin delta. The LMR GIS is being developed to provide the information needed to monitor the success of resource management efforts. The management efforts include: providing optimal salmonid spawning and rearing habitat; maintaining and enhancing the riparian corridor, conducting streambank revegetation projects, salmonid spawning gravel enhancement; and fencing projects to exclude cattle grazing along the river margins.

For the Lower Mokelumne River GIS project, there are six components in the structure of the Mokelumne River Spatial Information System:

1) System Configuration

2) Data acquisition / Development

3) Application Development

4) Analysis

5) Output (in the form of maps and reports)

6) Documentation (including metadata and a user guide).

In addition, there are two other variables being considered 1) The spatial extent of the study area, and 2) The project time frame expressed as short-term and long-term objectives.

The proposed spatial extent in the District's requirement document was perfectly suitable for the majority of studies but would not accommodate other studies with a direct influence beyond the 500 feet study corridor. An example would be the flood prone lands, which would extend inevitably beyond the study corridor. The proposed solution was a bi-level spatial dataset comprising of two sub-sets: 1) Regional sub-dataset and 2) Local sub-dataset.

The regional natural resources spatial dataset was constructed from existing 1/24000 scale digital and map data available, such as USGS, SCS, and satellite imagery data.

The local dataset was based on high resolution 1/4800 existing photogrametry data obtained by the District. The regional dataset is bounded by the natural watershed while the local has been clipped by the 500 foot study corridor.

The former dataset (1/24000) will have paramount importance in terms of the evaluation and assessment of any analysis in the context of the natural watershed boundary in contrast to the 500 feet corridor of the study area.

The project's objectives have influenced the project in terms of maintenance and temporality. To some extent, both are inter-connected. The long-term approach automatically recalls the maintenance of the project. This will imply two distinct terms, "upgrade" and "update".

The term "upgrade" is mainly attributed to the equipment (software and hardware) rather than the datasets. The six components of the spatial information system will be affected by the process of upgrading and updating. Ideally, the entire workflow will be audited recursively by the factor of time ie., every year. Not all the layers of information will need to be updated and upgraded every year. For example, salmon spawning and gravel deposition will need more frequent updating than the color Infra-Red aerial photography and vegetation coverage. Thus, a suitable upgrade-update schedule is being developed to meet the need of long-term maintenance.

Application Development

The application development is the key to precise and error-free operations and analysis. Similarly to spatial database development, which is an investment in information, the application development is an investment in knowledge and expertise.

The application programs will be developed

1) to ensure the quality of the analysis,

2) to invest on expertise and knowledge in form of programs, and

3) to write customized programs in response to the specific needs of the project.

The development has involved:

1) Meeting on regular basis with the project manager and team members to develop criteria and rules for a given analysis,

2) Translating the wish list into a series of algorithms,

3) Allocating software tools or writing customized programs to undertake these operations,

4) Coding (in AML, AWK, or C programming languages),

5) Testing, and

6) Debugging.

In general, application development will be approached as a process of abstracting the ideas in the form of spatial analysis programming language. The first stage was a pilot database created to ensure the quality of the program performance. Followed by the roll out of the full scale "production" database.

Analysis

The spatial database is an abstracted version of the real-world in digital form, and the analytical capabilities of a spatial information system provide modeling and simulation.

Based on the objectives of the project, sets of rules and criteria have been developed and suitable analytical tools were selected to accomplish modeling and simulation. The analytical tools included 1) overlay, 2) regression, 3)rule-based modeling, and 4) temporal simulation.

The customized application program command line interface for the analysis and modeling of the floodplain is as follows:

FLOODMODEL {minimum_mapunits}

Floodmodel application functions:

1. to detect floodprone and potential flooded areas.

2. to detect the effect of flood on the water table level.

3. to detect changes in two consecutive water releases.

4. to calculate area and volume of the floodprone and potential floodprone areas.

5. to identify future areas for salmonid spawning.

6. to quantify the amount of stream margin habitat suitable for juvenile life stages under specified flow conditions.

7. to provide a tool for developing a schedule of flow reductions.

8. to identify adjacent landuse practices.

9. to identify lands that may be acquired for public access for fishing, picnic/boat launching areas and wildlife viewing. 10.

to detect the extent of flooded area in the event of levee break down.

Contacts:

Joe Miyamoto, EBMUD Project Manager

Reza Ghezelbash, GIS Consulting & Application Development

Mardi Jackson, EBMUD

500 San Pablo Dam Road

Orinda, CA 94563

(510) 287-0459


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